Wow, Great project and build!
I had many of these trucks startng with my first new vehicle, a 84 diesel 2wd ram 50. 450,000 miles and wrecked, then another 160 or so before trading it in on a v6 4wd.
Got 450,000 with a 5th wheel hitch towing a 4wd 580K case backhoe on a triaxle gooseneck, once from Miami, at 55mph in 3rd gear at 4000 rpms all the way back. I did break the bearings after 120,000 miles, (running Amsoil), so cant complain really.
No oil use etc as new when sold! GREAT engine, IMHO. Oil was changed at 10,000 miles (Amsoil) and oil tested "as new" then. Trans and diff oil at 100,000 miles.

I'd put some "Energy Release" in your trans fluid IF its not worn out. This product makes oil seek heat. I have it in my backhoe and have not replaced a spider gear that was a biannual repair (undersized bearings) before I added it to the Amsoil in my transaxle. I still change it every 500 hours though, but much less "shavings" shiny things in the oil when changed. Its a GREAT drilling fluid if using it on tool or hardened steels, as well! Order off net...
I used and tested the stuff in airplanes and in all kinds of (my) equipment w/o oil starvation failure (yet. However, running an engine with oil starvation (centrifugal forces from doughnuts moving oil up side of oil pan and block away from pickup is ALWAYS bad...)