Mark,
I made this swap just recently. My advise is to keep the original rear end and change the ring & pinion. In my swap I used a 79 camaro rear with a full syncro 3 speed saginaw. The 3 on the tree linkage was a real BEAR. I took me a long time to fabricate the linkage using some parts from a MR. Gasket 3-speed stick shift linkage. It works but the shifter sometimes sticks. And the throw is shorter for reverse & first than second and third.
If I had to do it again I would just swap the ring & pinion. I could send you some pictures of the fabricated linkage. It might help you to make up your mind about which way you want to go.


The truth will set all men free.