[Bassman/NZ]

+1 for JWL's wonderful book. The book proves, and I have proved it to myself, that the best mod that can be done is to mill the heads to bring the squish area over the piston down to about 45thou. This provides a useful increase in torque, which is what you are looking for. Bang for buck, this is #1. Beyond that, changing rear end ratio and/or adding overdrive works well too, but is definitely not on the bang for buck chart!