Tate, would you send me a pm listing every detail of the engine. Your questions are good IF I knew what I was working on. I have no clue except what you have provided.
On a dead stock 360 smog engine I'd use a 750 all the way up to when I had my 10.5-1 360 with RPM heads and intake, super comp headers w/ 3 inch exhaust and a whopper of a cam, 4 spd w/ 4.10's.
A regular 4150 750 will do the trick on most any med. to large OE sized small block. Even better when built up.