Picking gears

Just got a 68 Valiant not too long ago
360/380hp create engine, 2800 stall 727 with 2.96 gears. I want to take it down the strip a few time with the 2.96 gears but looking to upgrade somewhere between 3.55 - 4.10 haven't narrowed it down yet.

From what I understand you should be 500 - 600 rpm over peak power at the finish line which would be about 6000 rpm with 4.56 gears.

My question I assume that performance gain with gears is gonna be non linear.
Like going from 2.96 to 3.73 is gonna be a bigger jump than 3.73 to 4.56 in performance??

Assuming 4.56 is peak performer in this e.g.
Plus what et and mph should I be able to run with the right gear ?