Gears or torque convertor

My mechanic feels I will get more pep or off the line performance by by having the torque converter rebuilt with a higher pounds opposed to going from 3.23 to 3.91 gears in the rear end. The car is a 64 valiant with a 273 auto, 4 barrel carburetor. I've never done either so what are your thoughts? I have a sure grip rear end and right now can't burn rubber down hill!