The converters stall rating would need to be used in connection with the cars weight, gear and tire size as well as useage. I think he can get away with as low of a stall as 2000, though 2300-2500 would be much better for driving around. A higher stall would be great with high gears and drag racing/street strip like quality. 2800 & 4,10’s w/27” tires.