replacement 12 bolt rear

[NovaMan]

Originally Posted by Alan Roehrich

Most all of the companies that sell rear ends use the KTRE housing for their heavy duty 12 bolt stuff. The KTRE housing is great, because it is thick, and stiff, and you can get it with a 3.250 carrier bearing bore, so you can use an aluminum spool and 35 spline axles.

It's interesting that you point that out. I was internet recently researching aftermarket 12-bolt options, and I wondered how many companies actually cast their own center sections.
The companies I looked at are Mark Williams, Moser, and Strange. MW says they use DTS Express/KTRE cast ductile iron center sections with cast caps, available with stock 3.062" carrier bores or larger 3.250" carrier bores for people who want to run 35 spline axles.
Strange claims they use a "Strange designed 12-bolt case with torque arm provision." It's nodular iron, and the caps are chrome-moly. They make no mention of carrier bore diameter, but they don't offer 35-spline axles in any of their crate rearend packages.
Moser uses nodular centers with high nodular content cast iron caps held in with 1/2" bolts. They don't mention carrier bores, and they don't package 35 spline axles with these rearends.
Based solely on that information, I think I would go with the MW/DTS/KTRE unit with the larger 3.250" carrier bore so I could use 35 spline axles. I also think it's cool that MW makes FED chassis kits and parts for '57-64 Olds/Pontiac rearends.