[mattjw916]

Fast by Ferracci still has them available:

http://www.ferracci.com/store/cart.php?m=product_detail&p=98

 

[mattjw916]

Everything is interchangeable as long as you have the proper fuel delivery and free time to fiddle with it.

Biggest PITA for engine swaps is the charging system IMO.

 

[mattjw916]

Right... the three stage vs. two stage correct? There is no simple way around it or easy way to swap one for the other?

Easy answer is match donor bike to donor engine, i.e. keep 2-phase bikes 2-phase. Granted if you have mad skills and time you can upgrade a 2-phase to a 3-phase but I prefer not trying to ice-skate uphill... it's very tiring.