[RustyTumbles]

I would go the 3.2m, I think the 2.5m may end up being to small for what you want to do. As for the engine a DA100 would be first choice, however you may have to butcher the cowl to fit it in and in doing so loosing the scale look. An 80-85cc will fit inside the cowl alot better and still give you good performance.