Need a 4-Speed

You can use a 4 speed out of about any A-body (Duster, Demon, Dart, Barracuda) 67 and up for certain. I think on the earliar A-body's things may have been different but not sure. Then it can depend if you want a overdrive or non-overdrive transmission. If you want to build your engine in anyway you'll want a non-overdrive and those can be hard to find, but they are around.