I'll have to take mine apart and see what size it is. I think it has an OS style NVA. It is a through the body venturi, and attaches to the engine with the same size screws that hold the R/C carb on. Drop Jim Lee a line and see if he has then all ready to go and has the spare mounting screws. I think I have gotten a couple from him over the years.
The .32 was originally a heli engine, and for airplane use, they just changed to a round head. The SX has a heli counter part also I believe. i have one with the big heat sink head, and need to find an airplane head for it, or just start trimming and hacking at the heli head one of these days.
Type at you later,
Dan McEntee
PS to add, that a Helicopter engine needs to make it's power in the middle to 3/4 throttle range for proper control, and that is why they make good stunt engines with out too much fiddling. Most R/C airplane engines are designed to run at full tilt boogy throttle settings, but you can't fly a chopper that way all the time.