if the wheels have 6 clips they're the older [pre-55] style that are 4.5 - 5", if they have 3 clips they're likely to be the right 55-59 wheels, which should be 5.5" [if 15's, I'm not sure on the 16's], and they will take tubeless radials [if not rotten rusty inside] ... look at shops that sell truck tires, there should be LT radials available in 16"
the later 4X4 wheels will work, but 8" would take a wider tire than is good for the front bearings and spindles and you'd hafta make sure those tires didn't interfere with the steering
Bill
