3/4 tons have plenty of reproduction parts. The bed wood, box sides, front box panel, running boards, aprons. 1 tons.... Not so much

The cab and sheet metal is all the same. Fenders front and rear, inners.
No experience with this yet, but they say that regular 16" trailer rims fit well on these hubs. I believe 215/85/16 tire size. Don't quoteme on that though as I haven't gone down this road yet.
As for gears, if the back pumpkin is an Eaton you can swap out you gears for 4.10s and get the speeds up. check out the Tech Tip link at the top. I plan on doing this too.
But if you're dead set on a 1/2 ton, I'd keep the 3/4 ton and keep searching. You'd be surprised what you may find. I would also recommend this advice: Buy the best shape truck you can afford. Bargains require much more work. I am much farther ahead on my current projects because I was patient and bought solid trucks. If you do find a 1/2 ton, you may be able to swap some "good" stuff from truck to truck. Get the good parts and perhaps then sell the 3/4. Good used parts for these trucks can be hard to find (especially where winter is harsh and salt is the answer). I have personally bought old "junkers" destined for the crusher brought them home and made quite a few bucks to put toward my own trucks. I bought a 49 GMC rust heap for a bottle of fancy whiskey and then proceeded to sell the straight painted grille, hood, radiator support and a couple trim pieces for $700. I took a few pieces that I needed for own trucks too. Once devoid of good parts, the crusher guys gave me $150 for it and picked it up. Many people don't want the whole truck, but do want a good used part.
Problems?
I picked up a 1950 1 ton in really good shape, I wanted a 1/2ton so I kept looking while keeping the 1 ton, found a very good 1/2 ton, and now I'm restoring both!
Storage- you need a lot of space. My part trucks end up at my parents' farm.
An understanding spouse.
Pros?
The parts trucks have generated about $1500 extra cash minus some effort hauling them home.
Having that extra truck has sure come in handy when I have forgotten how something goes back together.
I can't wait to have the big brute 1 ton and the elegant 1/2.
That big old 1 ton with the 9ft box and duals sure gets a lot of interest at shows. I've definitely been converted to the 3/4 and 1 tons. They have a special place.
Good luck!