The same small diameter 10 bolt lug pattern is used on a lot of 19.5" tubeless wheels, but those tires look a little out of place on the older trucks because of the low sidewall profile. To make the rig a "roller" while you're working on it, you might check out salvage yards that have a few retired Class A motorhomes in their inventory. That lug pattern is pretty common on the bigger motorhomes.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!