Re: 4 wheeler build-up
Well, I have been there and done that. The Honda 250x or 300ex chassis is the easiest and most cost effective swap. A little modification to the rear of the case, build a few spacers and its basiaclly done. The only diffcault step in the swap is the exhaust. I had one custom made to fit my bike.
Another possibility is the Honda 250r chassis. I am in the process of building one of these now. It is nore difficult because the frame will have to be modified to make the four stroke motor fit correctly.