John,

welcome back to the hobby. I believe that tuned pipes (TP) on 4 stroke engines are questionable in performance gain. I inquired on the same topic a year or two ago and was told that TP's are effective mufflers on 4 strokes (which are already quiet) but don't significantly change the power curve of the engines. The 2 stroke pipes are basically designed and sized for 2 stroke resonance.

I believe the designs that you want to build are of later classic vintage. You could probably power them with whatever you want (2s, 4s or electric) provided they have adequate power.

It would be interesting to see some snaps of the plans you intend to build from. That and specs would no doubt bring on a number of suggestions for power plants in the thread.

David.