8 1/4 rear question

Did this swap before, and just did it again in my '76 Duster this summer. I have another one I'm getting ready to put in my '74 Duster. 65-67 are the best for A-bodies, but the 68-70 are just about the same width.
The 65-67 just bolt right in? With springs from b body or u use the A body springs?