There are four different differential spring perches that Chrysler uses:
- The popular one (’60-73ish Mopar, 3” tubes) – which is what you see for sale everywhere.
- The FMJ spring perch, 3” tube (also used for other carlines after ‘73ish). This one has a large center-hole instead of a ½” center-hole. I don’t recall seeing this perch for sale, before.
- The 2.5” tube 7¼” F-body. Not many of these were made. They also have the large center-hole in them.
- The 1-ton pickup perches (Dana 70 or 80). Larger tube diameter and much larger/thicker perch.
Hadn’t seen the last 3 for sale before (well, I hadn’t looked for the 1-ton perch before, so it might be). The ones you want is the first one – which is the one for sale everywhere.
I would agree, get new perches and leave the old one alone. After welded on, paint them well so you will have decades of trouble-free service.
Note: the goal is to have them welded center-to-center at 44.46” (1,129 mm) and parallel to the centerline of differential pinion gear shaft.
If you are too lazy to figure that out (like I am), then remove the brake backing plate(s) and use the top two studs to determine level.
BudW