A very good plan.The tail lights I just want as spares. They're hard to find for the 80 and 81 wagons. LOL.
The perches were relocated for the correct spring width. It's all done. I am going to use the shock plates with the new rear. The rear that's currently in the car now is a 8 1/4 with a 3:73 posi. Works perfect. No noises or vibrations.View attachment 31930
A ’65-68 C-body (Fury) 8¾” has perches set at 46.00” center-to-center and is 56.750” flange-to-flange.
FMJ differentials (either 7¼” or 8¼”) has perches at 44.460” center-to-center and is 54.340” flange-to-flange.
If you had 1.0” cut off per side – that would be pretty darn close to perfect width wise, at 54.750”.
The perch width might be a different story – and might be worth to re-measure before install (white arrows, in picture above).
You might also perform a search using differential removal / install and my user name (BudW) for tips.
Do you plan on reusing the original ISO spring clamps or upgrading to the older style spring/shock plates?
One last thing, wagons came with an 8¼” differential. If yours is in good condition, don’t toss it. There are several members here looking for a replacement for their 7¼”one.