Tuned pipes have made quantam leaps since the era you speak about. We have come from 2 piece pipes held together with hose clamps and a piece of silicone tube and we would measure the bend in the header and lengthen or shorten the distance to the pipe joint. To chambered pipes, (2 and 3) and in recent years one piece pipes. (really two pieces but no silicone tube) held together with springs. Then you change the "tune" by using short, medium or long headers. Also now a days, pipes are used to tune to "short" or long tracks, and especially for fuel mileage.
I would go to the local track and see what they are using and why. You can't go wrong with novarossi and the pipes Shawn suggested are excellent.
Novarossi 2052 is also good, along with the new 3006. Good Luck!!