Most Acer species are quite tolerant of black walnuts/juglone, Acer rubrum included. I'd have more concern about trying to establish any tree in close proximity to large, already well-established shade trees like the walnut. There will be just a lot of competition for soil nutrients and moisture and he with the most well-established root system (the walnut) tends to win :-) I'd start with a smaller tree (easier and faster to establish) and provide a lot of TLC for a couple of years, primarily in the form of regular, deep irrigation. 'October Glory' is arguably the most popular cultivar of red maple and is widely available - you shouldn't have any difficulty in locating one.

There is not likely to be any problem with the gas line. However, the roots from the trees -- as a rough rule of thumb extend 3 ft in radius per inch diameter of trunk - clay soils, less if on sand. The problem will be more if the gas line needs to be dug up, or if the tree and roots need to be removed. THen working around either could be a significant problem. If that idea bothers you, then install a root barrier between the proposed trees and the gas line. Sink the barrier at least 4 feet into the ground, and let it sit a bit above the surface, and if possible, attach a copper strip at the top of the barrier on the tree side. Copper is toxic to the roots, and the roots won't grow near the barrier. The simplest root barrier would be plastic sheeting, such as used for damp proofing around houses.

John - no problem digging longer roots, except that you want to maintain the soil around the roots as much as possible (vs exposing them) to help maintain the small hairline roots - these are the roots that absorb water and nutrients and oxygen from the soil. And soil is heavy, especially wet soil in the spring. Digging around the roots, lifting the soil and roots, --and transporting this mass without it falling apart -- is a key problem. Access is usually difficult, beech seldom seems to grow near the edge of the forest (unless the area has been cleared) -- likes a bit of dampness , and when you are digging up your specimen, if possible you don't want to destroy other saplings. Generally, smaller diameter stems are easier to transplant, and have better survival rates - like 1 - 2 inch diameter. Larger stems demand a larger root-soil mass, and volume being a cubic function, weight increases fast. As others have mentioned, beech is a finicky tree about where it grows. It seems to prefer well drained soil, with a bit of dampness and deeper layers of humus with rotting leaves above does help with survival. I have seen Beech grow on clay -- with difficulty. Carefully examine the site where your specimen tree is growing, and try to duplicate it as much as possible for best success. And you want the newly planted root mass to be at the same level as the area it grew in., If you succeed, beech is a great long-lived tree. Sorry, I can't help you with mail order. I am based in Ontario, Canada -- well away from New Jersey, BUt, a local nursery or a landscape architect or a possibly a local arborist could name some good sources. If the company you normally deal with hasn't got what you want, it may be that what you want hasn't got a good survival rate, or such a good survival rate, there is no point carrying the species.

Unless you say otherwise, I'm presuming that you want these to be single leader, straight trunked trees ...? And that when they're full grown, they'll be many tens of feet tall ... 50', 60', 70', etc....? And that they'll have a canopy whose bottom will clear the ground by at least 10' or more ...? If all that is true, then every branch that exists now will not exist in the finished tree. Relative to that, their only truly important function now is to capture sunlight to feed the main tree, especially the trunk and root system. Only the trunk and roots will exist and therefore, it is the important thing to focus on. A main thing to watch out for is the development of competing trunks that originate during the first several years of the tree's life. Any branch that has vigor and whose direction of growth becomes more vertical than 45*, poses a danger of becoming a competing trunk. I see such a branch in the first picture, coming off of the trunk toward the right, beginning lower down. (Some other pictures have similar situations.) This is nothing to fear or necessarily want to get rid of immediately, because it has a proper role for a while as one of the tree's food factories. But before it gets too large, it must go. If you adopt a general practice of removing the lower branches from a tree as it grows, whatever problems they could potentially bring would be gone as well, resolving the problem of having more than one trunk for example. (BTW, once you get within the adult tree canopy itself, I don't think it much matters that there are multiple trunks. They're not compromising the looks of the tree anyway.) A person can obsess about all kinds of details about plants & their maintenance, but what I find is that doing so tends to get in the way of maintaining trees at all. People don't know when "the best time" to prune them is, so they figure that NEVER is super safe time! In a very general sense, I like to prune woody plants (trees and shrubs) in late winter/early spring BEFORE the new spring growth occurs. But that time could really be extended to anytime in the fall after the plant has gone dormant, which is a huge window of pruning opportunity. Most people don't want to prune in the winter because they think it's not the best look and it's not going to be cured until the plant grows again. If pruned in early spring, the growth happens right afterward and fixes everything. There are some big advantages to pruning in the winter: it's not too hot ... and it can be an unhurried time when there are not other yard chores demanding attention. [Here, I must mention that there are two main divisions of bloom when it comes to woody plants: those that bloom on new wood (current year's growth) and those that bloom on old (last year's growth.) Don't prune plants that bloom on old wood after they've set bed (which is often not long after they bloom.) If you prune them in fall, winter or early spring, you'll be cutting off all their flowers for the current year. Plants that bloom on new wood are more forgiving and pruning anytime from fall to spring usually works ... but just once per year. If you don't care about the flowers of a tree or shrub you can prune anytime. Another thing, the main reason the annual pruning of most woody plants occurs sometime during dormancy is because the spring flush of growth will be forced to put all of its oomph into whatever of the plant remains. If one waited until after the flush of growth, and then pruned a lot of the plant away, they're only going to get a smaller portion of it back. Back to pruning off lower branches, my rule of thumb is to remove all branches that emanate below the middle of the tree's total height ... the lower 50%. That leaves you with half the tree looking normal and half of it is trunk. What happens right afterward is that the tree grows taller and branches more. Within a couple of months of branches being only at the top 50% of the tree turns into them being in the top 60% or even more. If It's a good year, and the tree has water and fertilizer, it could easily be back to a ratio of 70/30 by season's end. The net effect is massaging the tree into upward growth, while inadvertently fixing branching errors along the way.