We have found a few different offers, can you recommend any or specific specifications we should look for?

Have you ruled out porcelain tile that looks so much like pine that you'll have to look twice or 3 times to see that it isn't real wood?

Susan, I do not personally work with any but do look for a moisture content of between 6% to 8%, any higher in most pines could result in excessive expansion and contraction showing larger gaps between the boards in the dryer times of year, typically the winter months. There are a lot of manufacturers that only dry to 10% to 15%, I would stay clear of those. Also look for plantation or farm grown hard pine as these are certainly better for the eco system and are harvested from managed timber with the environment in mind. Lengths of up to 10 foot to 12 foot in hard pine are good, any longer could result in installation problems.

The wear on your flooring greatly depends on the finish you're planning on using.

We always recommend 3 coats of oil-based polyurethane for a quality, durable finish.

https://theflooringblog.com/what-are-different-types-of-polyurethane-finishes/

https://theflooringblog.com/oil-vs-water-polyurethane-finish/

Longleaf Pine is generally recognized as being among the hardest but at a Janka rating of about 870, it's significantly softer than Oaks that are often used as a benchmark (at 1260 to 1360 rating).

http://www.wood-database.com/wood-articles/pine-wood-an-overall-guide/

Johnson Flooring is correct when tesing the Janka on wet green (not kiln dried) lumber, which is the method used for Janka hardness. When kiln dried to 6% to 8%, longleaf heart pine gets much harder, up to 1225 to 1400, depending upon the sample used. Without getting anymore technical and not wanting to bore the reader, it all has to do with the woods cell structure and whether it is an open or closed cell wood. In closed cell woods, like longleaf pine, the cells collapse as moisture is removed and will not expand. This process stregthens and hardens the wood as the moisture content drops, making the longleaf pine much more dence. In open cell woods, such as oak, the cells remain open and do not collapse as the mositure content drops. Unlike longleaf pine, oak does not get harder because the cells remain open and the cells tend to crush together under pressure. So as far as hardness is concerned, the drying to 6% to 8% has much more of a positive effect on longleaf pine than oak and other open cell woods.

Do you have a source quoting the hardness of dried pine? I couldn't find anything.

Forest Products Laboratory

Have you looked into hickory? Hickory is widely used in most engineered products due to its availability, low cost and high rating on the janka system. It rates higher than oak.

We have considered but a have learned through researching hickory flooring that it seems to be the number one claims issue for buyers. Even though the hardness factory is good, hickory is said to also be brittle and apparently easily splits on the ends and within the middle of the boards more frequently than others. It also seems that the longleaf pine does not have issues of this type. Thank you for the suggestion but we are sold on the longleaf pine, its look, and history for being used, and lasting for 100's of years,