Harry, you have a good start here but I have a few things I would like to point out.
1. The bike seems very short. When I was a the motorcycle museum a few weeks ago I measured a lot of bikes and the shortest I found was 82". That was a 1923 hd flat track racer. every thing looks fine on yours but I think the middle of the bike could be a tad bit longer. I think mine is around 32"
2. The top tube angle looks a bit awkward, I have found on most bike the angle of the sloping part of the top tube is about 20 deg. Some have more but 20 seems to be the minimum. I find that the lesser the angle the more options you will have when you go to mount the seat.
Please don't take this criticism the wrong way. I want to see this build become one of the best on the site, and I am only trying to help you see the potential of the idea you already have.
We have a saying in the art world "don't be afraid to kill your babies."
sometimes you have a good idea but the one you have after it is always better. Keep up the good work.
p.s. I think you should try and fire that engine up. If it spins freely what have you got to loose?