['68OrangeSunshine]

To be honest, I never tried my '68 rims on my Jimmy. The Stepside's OEM 6-lug rims were 5.25 x 17.5, and originally came with bias ply 7.00x17.5 tires. Then they got scarce and I went with 8.00x17.5. Then I went to radials, R8x17.5LTs. Then the tire shop said my OEM 17.5 rims were shot [and no longer available,] so I went to 235/85/16LTs on 16 '' rims.
The Jimmy came with 33x12.50x15LTs on 15x10 rims, when I got it. I used to run a '67 K/10 Suburban with 33x12.50x15 tires on 15x8 rims. When I tried to swap over the Jimmy's fresher tires and rims onto the Sub [when the Jimmy needed a new engine] the rims fit, but I could not turn the wheels much as the 10'' rims interfered where the 8'' ran OK.
The '67 had drums up front, the '71 had disc. I don't recall the type of brakes being an issue, just the rim width. But that was about 20 years ago.
Maybe some others have a wider perspective.