Those are rally wheels. They were used on Corvette's, and just about all models of Chevy's in the 60's and 70"s.
That truck has been converted to later model front hubs and likely a later rear end. They are likely a 5 x 4 3/4" bolt pattern.
There are no stock 46 hub caps that are going to fit those wheels. Aftermarket wheel suppliers like Wheelsmith and Vintique can provide modified stock hub caps to fit the later wheels. I personally think they look good on just about any car or truck.
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine