Just thought id mention it. would hate for you to go through all the work to burn it up. I know sled motors are used in all sorts of machines made in backyards across the USA. If setup right they can be dependable and outright narly on a cart or other machine. Alot of the time though you see these homemade machines dead on the side of a shed or in the back 40. I wouldnt reccomend to anyone to just drop a sled motor into to something and run it without looking into the jetting. It will run, may last for alittle while, but its a ticking time bomb waiting to blow at anytime.
none the less i think what you are trying to do is awesome. Sure is a big undertaking to fit that motor in that bike. Food for thought.......ever thing about turning it into a trike? that should give you plenty of room and would be bad ass.
And yes if you are running a tilly then you have the ability to adjust your settings. a mikuni on the other hand.........you bet get the right jets!
P.S. That cart is awesome!!!!! nicely done!!!!!! she must rip pretty good!