Hello, I thought I had real nice rims for my 1933 Chev 1.5 ton so I went ahead and bought 6.00x20 tires ,tubes and flaps, Unfortunately only to find out that when I pulled apart the old tires the rims a rusted away junk so I need 3 or 4 locking rims with 10/7.25 stud circle with-5/8ths holes and a 4.75 center hole I live in SE Wisconsin
First tubeless tires came out in the late '50's, 22.5" rims with that bolt pattern on GM trucks are available, hard to find, look on farm trucks, need to make spacer sleeve to use the modern wheels with slightly larger hub mounting hole. Modern 9 x 22.5" tires fit OK.
Unfortunately you have a set of 20's, perhaps you can find someone who needs them; only other option is to keep searching for good 20" wheels.
While you are looking for 20's, keep an eye out for some 22.5's, might take a while for either. Sometimes one finds one or two mixed on a truck.
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires. '47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle. '54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed. '55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
They are tough to find. I need three as well for my 40. The shipping kills you if you can find them. I have run across wheels but they are the RH5 or split rims not lock rings. I always have asked for good photos. That tends to stop progress.