360 Carb input

650 for a mostly street driven application, for the track, A 750 for the max power out put. The differance will be approx. 10-15 HP.

The 360/380 create engines routinely dyno'd 410-415 HP with a 750 & 1-3/4 headers.
If your running the track mostly, with parts like 4.10'or numerically high ratios and high stall converters, then the 750 would be very good to use.
Less than 4.10's and on the street more often I would suggest a 650 for a ran crisp throttle response. FYI, The 750 on the street is doable.