Most fruit trees (at least the commercially grown types used for food) are cultivars. They are usually grafted or budded onto rootstock.

Some fruit trees (like many types of apples) most often produce seedling offspring very different from themselves. Others (like most pawpaws) can produce seedling offspring fairly similar to the parent. I don't know of any fruit tree cultivar that would produce seedlings that would really be considered true to type, but the degree to which they are similar will vary from different types of fruit and will vary between varieties of the same fruit. Cultivars have unique characteristics or they wouldn't be cultivars.

You give your zone as 6b, but you might want to provide more information about your location for better advice about fruit trees. Different parts of the country have very different growing conditions. The zone is important, but doesn't give the whole story.

Most citrus (but there are important exceptions) grow true from seed, meaning genetically identical to the parent tree.

Many peaches will grow fairly true, meaning the fruit will be much the same. Probably the older and less crossed the selection the truer it will be (by having a less diverse ancestry).

I've grown a lot of Italian Plum from seed. It varies a bit, but the seedlings are not much different from the parent. Also have saved and planted seed of an Italian x Damson plum and they tend to come out more variable, with the Italian char. dominating.
Have heard that Golden Delicious Apple comes close to true but it is a scab prone variety and I don't recommend it.
Grapes are highly variable, especially if the parent is a French hybrid of multiple species.
some may be good, (about 10%), and the rest are not .

chestnuts, if you like nuts.

Basically, if you want to know the trees that grow truest to seed, think of self-pollinating types. It was mentioned peaches. Peaches are a good choice. Most are self-pollinating. Of peaches, I've read Elberta is very true from seed. Tart cherries also come fairly true to seed. I've not heard how true from seed European plums are, but my guess is they are. Things that generally require a pollinator are going to be less true to seed. Apples, pears, sweet cherries, etc.

>> Tart cherries also come fairly true to seedHave done test's on Evans Cherries, not one plant have produced more then 2 or 3 cherries.

Mexican Plum is a native tree that is rated for Zones 6-8.
Its planted in Texas both as an ornamental(orange fall color/spring flowers), as a rootstock for grafting, and as a plum source. Plums are about an inch in diamter and fair. Tree is hardy and drought-resistant. Fruit is basically a slightly larger version of wild plum bushes.

Speaking of seeds, does anyone have a Montrose Apricot?
I'd like to grow a few seedlings of that one.
Would be happy to trade for a few Damson/Italian Seedlings.
I like the Damson Plums for Jams because they have a very strong flavor that doesn't cook out. Also, they are a bit smaller trees, "usually", than the Italian Plum, which is not too big of a tree either.

Hey boizeau. Are you still on here? I’m looking for some Damson seedlings.