I have an Eaton posi on the 12-bolt rearend of my '68 C/10. I think it came off a '69 GMC stepside. Eaton made the positraction axles for GM in that period. I had a differential shop rebuild my 12-bolt on a '67 K/10 Sub, the original axles wore out and for some reason I couldn't get GM parts. So I went with Moser custom alloy axles and an Auburn posi. Spendy, but results were good. Then, after I bought my '71 GMC [K/5] Jimmy, I was pleasantly surprized to find it had a factory (Eaton) posi.
The '68 C/10 pickup has a 292 and it works good with a posi.
Also all 3 trucks have 3.73 ratios. The Auburn I got from ProGear in San Diego.
