With a 383, the stroke will more than make up for any loss of low end on that motor. What kind of car are we talking about here? In a light mustang you would never notice any loss in low end torque. I had a friend back in high school that ran a cartech box on his 5.0 (92 fox) and that thing was a bullet. He had 3.73 gears and he got out of the hole QUICK. One nice thing about them is that they will fit a efi 64-73 mustang without going to a specialized export brace.

Dont worry about the small loss in low rpm torque...unless you are putting it in a galaxie.