I've been thinking about a t56 too. Just wondering how much power a t56 out of a mid 2000's GM will take. I know if you cough up the cash there's a gun on ebay selling t56 magnum's for around 3k, supposed to be good to 700ft-lbs or something like that. Another option would be a tr6060 out of a challenger or newer camaro.

I probably wouldn't want to run a .50 overdrive gear without port fuel injection. A carb might not be making enough vacuum at that load/low rpm for efficient fueling.