I see there a lot of aftermarket lowerdrives but they all say they are for K&B or Rosi. So I was curious if I could use one of these lower units with my O.S. 21-RGM that I already have.
Most of the aftermarket lower units are made for the K&B powerhead because they're plentiful, like small-block Chevy's. The Rossi's, Nov Rossi's and others have their back plate made to fit on the K&B lower I don't know of any made for the OS yet but with the growing popularit of them, there could be some in the near future