You would have to change pretty much everything on the bike to install an engine that is more than twice the displacement having significantly more weight, horsepower, and torque. You might be able to reuse the headlight, bars, tank, and seat with minor or no modifications. I'm thinking it would be an effort that would take a professional customizer many months of effort.
I'm thinking that most folks would have a higher chance of success and less cash outlay to start with a bigger bike that already has the engine they want. They could then bolt on the accessories that would make it more like the Street Rod.
