i just bought a 79 elky and i'm going to fully restore it. But i want to swap my 3 speed for a 5-speed manual.... anyone know if i can do this and keep it original. Does anyone have a better tranny in mind for my 79???

The only way to keep it original is to keep the original transmission, if you change it it will no longer be original. If you want a 5-speed upgrade a BW T5 is a good choice.