A 1912 Harley sold at auction in 2011 for $115000 There is no way I would be spending that amount.
I then came across a bike called a whizzer, made in the US, between 1939 to 1965 but they look much older, I spoke to every motorbike nut I know none them have ever heard of a whizzer. (very rare in Australia) and when I showed my 90+ year old neighbour a photograph of one he said, he thought his dad had one when he was a kid and it was old then! Perfect! if I can fool him I should be able to fool some more people at the car show!
After a bit more research I found that a company in Taiwan has started making replica engines, and the frame is almost Identical to a schwinn beach cruiser bike.
Looks like everything got a whole lot easier, and less expensive.
If you have a look at the photos on this step you can see whizzer engines fitted to different frames.
as requested here is a video of the finished bike,