RE: Engine Choice.
What about something like this? [link=http://cgi.ebay.com/NIB-OEM-SH-21-Buggy-Engine-ABC-W-Pullstart-2-4hp-RTR_W0QQitemZ6047304950QQcategoryZ34062QQrdZ1QQcmd ZViewItem]SH .21 OEM[/link]
I know that parts would be hard to come by, but considering the price, I'd consider it a disposable.