I tried to use the 49-52 passenger car wheels on my 56 when I did the disc conversion. They have a similar center section with clips like the truck but would not work. I subsequently purchased some after market wheels from Wheelsmith in Santa Ana, CA. They are dual pattern (4 3/4 & 4 1/2)commonly refered to as smoothies. They have a center that is similar to a rally wheel. He also took my stock caps and cut off the part that presses into the wheel and replaced it with a smaller ring. They have been on the truck for about 8 years.
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