Say a 250'x250 (acre and a half)?

I have an experiment going in my front yard for fruit trees.    But if it goes well, in a year or so I could be persuaded to maybe utilize some of the pasture land behind my house to put in a small orchard.   Nothing real huge but enough to plant 100 or so trees.  Call it planning for retirement.

Unfortunately, it is pretty high pH (tested 7.7pH) and somewhat clay-ey soil.   So I'd want to modify it a bit.

Ideas?  I've got a kubota L3560 with a front end loader and I don't mind doing a little dirt work.

You should not delay planting the trees you want.  There are some soul treatments for clay and you can add potting soil, top soil etc around the roots when you plant. I’d be planting a lot of pecan trees if I was still there. Pomegranate trees grow I. central Texas. If your South Tx you may be able to grow citrus.

Just spit-balling, I would think about having a dump truck load of top soil and 1" stone delivered, lay out your plot and drill 4" holes as deep as possable with a post hole digger on you tractor, mix the stone and top soil with your bucket and fill the holes where the trees will go.
Well drained soil is important.

I don't know how deep your clay layer is but anything you can do to get the soil better will pay off later.

Modifying the soil for shallow root crops is different than modifying it for deep root trees.  That's a big area that would be expensive to do anything significant.

I would recommend digging a bigger hole when you plant the tree and add good topsoil around and below the root ball.  Then maintain 6" of good mulch around the trunk.  Pine bark is great mulch and will help with the pH.

You said clay.  How well does it drain?

4 tons of gypsum to start on an acre  should help to loosen the soil.   You may need more gypsum than that but you can apply it over a couple of years. You also will get calcium out of the gyp, fruit trees are calcium whores

Elemental sulfur will drop your ph. Your soil test should give you the amount of sulfur to get your ph down to desired levels.

Not great as far as the composition of the soil itself goes.  It does drain but slower than the recommended "hole" test.

The topography does allow for water to run off, tho.  At least in the part of the field I would plant.  

I've got 7 fruit trees planted now as an experiment.  I just did individual hole modification for those.   Part of the experiment is also adding sulfur over time and testing to see the effects

Citrus grows well in south Texas but we do get occaisional freezes.

I have a meyer lemon, a key lime, and a satsuma orange in big 25 gallon molasses tubs so I can move them into the garage with the tractor during a bad freeze.

I would do pecans as they seem a little more resistant to things like cotton root rot but they also need ALOT of water.   Whatever I plant, I'm going to have to irrigate but the scale of water required for pecans seems next level compared to something like apple trees.

Your local ag extension service can give you great feedback if you give them a soil sample and tell them what you're thinking.

This^^^^^

I'd also lay out the planting rows, work them deep with a turning plow and apply/turn the gypsum in only those rows.

You could also see if a tree trimming company can dump you a load of woodchips that you could compost then add to the rows to give them some organic matter. It improves the tilth of the soil.

Gypsum breaks up the clay and provides good drainage, I've used it here with great success. I used to go to my local Lowe's and get the "stickers" that are used under the bundles of sheetrock. I'd leave them in a pile out in the weather and allow them to break down a little then spread them and rototill it into the soil. Worked perfectly.

I have a tree company that contracts with the local electric utility keeping the rights of way clear. I set up a spot for them to dump their chips for free and I usually have 20,000 to 40,000 cubic feet of woodchips composting in various stages of decomposition.
The chips break down into rich dark soil.
I turn the piles with a front end loader and mix some old stuff with the new stuff to get the microbial action going and to try and keep the piles at a certain moisture content.

When viewing the piles on a cool or cold morning and there's  steam plume above them, all is well.

I've planted in this woodchip soil for several years and it produces excellent cukes, squash, tomatoes, sunflowers, beans, peppers, lettuce, cabbages, kale and collards.

Start amending your pasture in the local spots where you want to plant the fruit trees first and work out from there. Everything beyond the drip line of the trees is just going to be grass you'll have to mow so concentrate on the tree locations.

When planting the trees dig a big hole and apply lots of well composted manure to give the tree some nutrient and a loosened area for the roots to expand out into.