You can sell that frame to someone in a state that does not require title Just a bill of sale and take the money and buy a titled frame, swap all the components out and bang you got a titled 450.

500's are a lot or work PERIOD if you have a strong runner.  You could go street bike motor in a quad but that's lots of $$$ and time to build it right. 

IMHO the bombusa is a kick Arse bike for big guys but it's lots of $$$