Remember if you decide to use a 727/518/46RH trans, you either need to run a manual valve body, or figure out trans linkage for the 1-2 and 2-3 shift. Only the 3-4 shift is hydraulic on the 518/46RH and electronic on the 46RE. Bouchillon has an adapter kit for the throttle pressure linkage. This takes care of the 1-2 and 2-3 shift. In my opinion, if you run a modern engine, put a modern trans behind it.