1968 Cuda 8 3/4 rearend axles

I sent used C-body axles ($35 swap meet) to Moser and they shortened and resplined them for $85.
The VERY NEXT day after I sent them, one state over, they called me to clarify usage. I told them over the phone A-body 8-3/4 with B-body brakes. (10" X 2-1/2") They knocked them out same day and the whole thing was 5 days door-to-door. This was about 10 yrs ago.

I measured the "new" axles and they were both exactly 28" from outside of flange. I plumb-bobbed to the concrete floor before and after. and it added exactly 3/8" to each side, 3/4" wider track overall.

It's not just wheels, but involves tires, brakes, etc. I pieced together the parts ahead of time getting swap meet B-body backing plates and new drums, shoes and hardware

You can redrill your flanges to 4-1/2 but then you have to redrill the drums and you'll always have bastard parts. If you search for 8-3/4 axles, most C-body, station wagon B-body, B vans and some 70's trucks are donors. You need a full 28" in length before the axle tapers down.

Your best bet may be to call Moser or one of the other suppliers.