Firebikes has probably the sexiest new bicycle available today, I've heard that you might be able to get them with motor mounts for a Chinese engine. Vintage straight bar "tank bicycles" or "motor bikes" which were bicycles styled after motorcycles around that time are a bit hard to find. They are very collectible thus quite expensive. The tank unit alone can also be hard to find and very expensive. I too was looking for one to make into a motorbike but finding one in bad enough condition and a common model was quite a chore. The cheapy way is to find a womens cruiser, remove the top most frame tube and weld on the top tube of your choice.
your looking at 40's 43-48 the rack is incorrect I believe. The tank and front light are very hard to come by so I think you got a good buy I have some strut bars for the front possibly. The chain ring doesn't look right either