Is it the ten bolt motor wheel, two ton Chevy bolt pattern? Or the slightly more available six bolt pattern? I second just running the old tires while saving up money. It's a buy once, cry once situation where today buying six new 22.5" 10 bolt pattern wheels is north of two grand for the rims; however once you have the rims you can find good used tires for $100 apiece if you're patient.
Back in the day, it was pretty common to upsize from 7.50-20 to 8.25-20 as the taller tire was easier to find, and gave a little boost to speed or fuel mileage. That was the first thing my Dad did when he bought his '65 C60 back in 1976.
Here's a modern radial ply 8.25-R20 tire
https://simpletire.com/brands/power...top-pick-top-picks&pick=most-popularIf your rims are still good you can reuse them, and gain the benefits of radial rubber if you intend to drive it very much.
