Re: Shift Improver Kit and Torque Converter
A shift improver such as the j-mod or trans-go kits will extend the life of the tranny, reduce sloggy shifts, and firm them up. These improvements will result in better acceleration due to crisper, firmer shifts.
If I remember right, an aftermarket torque converter(stall converter) will help you reach the power band quicker. More peak torque equals better launches.
A modded sixer would probably benefit from one in the 2500-3000 range.
Someone with more experience with them could add to this.