Ok, that clears things up. No-Spin is the same thing as a Detroit Locker. It is what's causing the issues turning, too. Just from the description, you do have the HO52, which was the oem diff.
For the trans, and MY6 from an early '80s Chevy/GMC would be the easiest bolt in, the NV4500 is another good choice, but will require an adapter.
