As far as getting rolling from a stop, I think you can do it with either rear. I run the TKO 600 behind a 496 with warm cam (243@.050 intake duration). I can get it rolling OK just above idle with 3.23 rear if I want for street driving. "Driven in anger" I walk it out of the hole at around 2000 RPM with 200 treadwear handling tires and pedal it to prevent smoking the tires.

I am running the .81 OD. if you are running the .7x OD you may want or can get along with higher numerical rear ratio. I think either ratio you are looking at would be fine. It would help to graph speed vs RPM with the two choices to get an idea what might be nicest for your driving plans.