8-3/4” axle conversion
No, you're not overcomplicating it. If you're using DoctorDiff 5x4.5" axles they use the standard Mopar BBP axle flange offset, which is different from the SBP flange offset.
Which means you need the entire 10x2.5" drum brake set up, including the backing plates. You can't reuse the SBP backing plates.
You can find backing plate measurements here Converting rear drum brakes from SBP to BBP , which will also show why you can't reuse the SBP backing plates.
You'll have to find a set of 10x2.5" BBP backing plates.
No, you're not overcomplicating it. If you're using DoctorDiff 5x4.5" axles they use the standard Mopar BBP axle flange offset, which is different from the SBP flange offset.
Which means you need the entire 10x2.5" drum brake set up, including the backing plates. You can't reuse the SBP backing plates.
You can find backing plate measurements here Converting rear drum brakes from SBP to BBP , which will also show why you can't reuse the SBP backing plates.
You'll have to find a set of 10x2.5" BBP backing plates.