The G26 size is kind of stuck in the middle. You will probably have to look into a 50cc size if you want to go gas in a WWII era plane. The door is wide open once you hit that size but mostly for plans built, you can get a short kit cut for most plans. About the only production kits avalable are the Top-Flite giant scale warbirds and they are all 50cc class. There are a few top dollar composite kits available for the 50cc+ class but you will pay dearly.
Good Luck!!
Anthony