Way to go
When I built my first frame I bent it around a tree trunk, you are way ahead.
Look for an old pre-unit motor of any brand, flat belt is cool. A t head gravely would be great, magneto too. It doesn't take a lot of HP to have fun. Hope you baffeled the gas tank. I have a pal that has built 20 plus pre 1915 bikes from a few original parts. I have most of a 12 Indian belt drive motor, I better get to work. Keep it up