The one thing I know about rear ends is that when they go out and lock up on you, its no fun. This is why I have never touched gear swaps, or any diff for that matter.
But im over my fear of screwing it up and locking the back wheels solid..I have a 69 Torino, just a lil 302 and c4 in it. It has the 8" with a granny 3.00:1 gear, and actually I can still do a burn out, and freeway cruising is at a nice low RPM. I think 3:55's would wake it up just a little bit and not kill my freeway fun. Here's where I need help, if im not mistaken I should be able to pull a 3rd member out of a 3.55:0 ford 8" car / truck and it should be a direct swap right...or should I just look for a complete axle, or maybe a 9" swap. ??