I get you, truck tires are very pricey, I've done pretty good finding newer take offs, guys swap out perfectly good tires for giant size. Also switched to Ford 8 lug rims from old splits. May try Craig's list for good used tires. LT235/85R16 Goodyears.
Best of luck

It's easier to get forgiveness than permission!
1946 1/2-Ton Chevy
1953 Chevy 3/4-ton Factory Stakebed