I put an Auburn posi on the 3.73 12 Bolt rear in my '67 K/10 Suburban around 1995. Sub was rigged with a 454 BBC/TH350/NP205/ on 33X12.50X15 meats.
In late 1998, it had an engine fire, and I towed it home. It sat until 2012, when I blew up the factory 12-Bolt Eaton posi under my '71 GMC Jimmy. So my drinking buddy and I cannibalized the Auburn posi 12-Bolt off the Sub and fit it on the Jimmy.
Yes, there were spring perch issues. The shorter [width-wise] '67 Rear went on under the '71 OK, but we could not get the narrower-width springs to stretch out to mate up to the '71's Rear.
The Sub's Auburn posi rearend still works great on the GMC, until I can get the factory Eaton Rearend rebuilt and back under the Jimmy.
If anything the narrower stance gives the Jimmy an even tighter turning circle.
The first step to the Suburban Rebuild Project, will be to rebuild the Eaton posi.
The '68 C/10 Stepside, L6 292/SM465/12-Bolt 3.73 w/Eaton posi has been running good for 34 years.
