B body rear, drum to drum
'62-'63= 58 1/2" (And '64 Max Wedge)
'64 = 60 7/8" (Exc.Max Wedge)
'65-'67= 59 1/2"
'68-'70= 60 1/8"
'71-'74= 63"
'71-'73 wagon= 64 3/8"
A body rear, drum to drum
'66-'72= 57 1/8"
So, yeah, about 3" per side. That's going to be hard to deal with. You'd need like a 7 1/2" backspace rim. Or get it shortened to A body specs.