LT-40 ARF Balance vs engine
I have an LT 40 and put the OS 46 LA in it, but I still needed a lot of lead in the nose, so I'd go with the heavier engine. I don't know how the plane got so tail heavy, but it took 10 oz to balance at the recommended spot for newbies. It flies just right though. My instructor flew it without any trim on it's maiden voyage.
Kerry