Moken, I just started assembing my speedster and I am using a G-38. There will be holes cut in the cowl for the spark plug and velocity stack for the carb, of course the pipes for the bennett muffler. I also picked up some 4.5'' wheels at the Perry show and replaced the tailwheel mount with one of bennetts. I was worried about that thin firewall and added a piece of 1/4'' lite ply. The prop came forward a hair more than needed, but should work ok. I also talked to Ray at kangke and he swears the firewall doesn't need any reinforcement. Bennett also sent me the linkages to operate the throttle and choke. This is really a nice arf, and I'm sure it will fly well with the G-38.