I don't think you really want to do that. I am not an expert in this area by any means but I have gained enough knowledge to know that this would not be a good idea. I don't think the GP Chipmunk is a good canidate for a conversion engine because of the small wing surface area. The plane is not really designed to use a gas engine. It will be too heavy with a big 5 lb gasser on the nose. I have no doubt it would still fly, but it would feel very heavy and landing it would be interesting to say the least. I think you would be better off with staying with a glow engine on this plane. If cost was not an object an light weight RCS 140 would be a good gasoline engine for this plane.