If you do a search, I have posted my two cents in the past as to how to kit bash a plane into a twin that is easy and quick.
Pick one with a long tail moment and large rudder. I have seen twin long Johns, Various "Sticks", Kadetts, ect.
If you cannot find the older posts, let me know and I will post here again,
Good luck,
Twinman
PS Good move on waiting on the P-38. I did not. Been there, done that DON'T. You are taking the correct procedure. They GO FOR IT. Nothing is so cool in the air as a P-38!!!