Jim
You need a converter that will keep the engine in the meat of it's torque curve the longest.
I had an 8 inch 5500 stall that would flash to 5400 at the hit, and drop to 5250 on the shift to drive.
I had a 9 inch 5000 stall that would flash to 5100 at the hit, and drop to 5000 on the shift to drive.
The engine would go through the traps at 6400 regardless of whether it got there at 1150 feet or 1280 feet, that's all it had.
The 9 inch was a tenth or better than the 8 just about anywhere except Denver!