Lenny will get it right, probably a fairly tight 8" would work the best, maybe 5000-5200 and flash to 5600, if you put that same vert behind your old small block it would probably FB to well over 6K...the thing to remember with converters is it's all relative to the motor/torque they are behind.

Again my only point is with a big block 4.25" stroke the torque is so broad and flat to me it becomes a question of how you want it to feel when you drive on the street. I would personally give up a tenth for a more tractable cruise experience, especially in a nose heavy BB A where TRACTION is going to be the biggest issue. sometimes more grunt (not necessarily Peak torque grunt) is more fun and controllable, and I know even high stall converters can feel "kinda good" but not "great" like truly feeling the motor use all the torque to pull the car from out of the basement. Roll on torque from all over the power curve to me is the most fun part of a big block street car, but I'm spoiled driving a 2400 pound 427 Cobra replica with a manual trans...I like all my street cars to feel as close to that as possible.

When I'm at the Strip I like to drag race but when I'm on the road I like my cars to feel more like a Road Race car, does that make any sense? Probably not.