Dyno'ed My 360..it's a pig..what next?

750 would be too big for the street but for the dyno it might work. If you want to replace the carb and keep it on there for street driving use a 650 VS holley at least those don't take an hour just to do one jet change.

You don't need to drop $10k on a new engine, take it one step at a time... figure out the leaning issue, then try a slightly bigger carb.

After that i would just swap the heads and cam together; nothing crazy just something like Mike from MRL said, decent inexpensive iron heads but with 1.88/1.60 valves and a good valve job and put in a modern cam not that old lazy Chevy grind copycat. You will pick up power and torque everywhere and probably some MPG too, all for less than $3k... probably less than $2k if you do all the assembly yourself.

That 727-based trans will suck noticeably more power than a 904-based one FYI but you have what you have and like you said the overdrive is a great feature to have in a cruiser.