Go for it! Schwinn OCC is a worth while build and looks so cool! I got my motor mount and exhaust from Bike Barry via Ebay. And I got my rear sprocket and sprocket adapter from Manic Mechanic/Creative Engineering. Livefastmotors also can provide these as well.
Barry is currently running a listing for his exhaust on Ebay. I agree, these are loud just like he says they are. I installed the baffle that he sells and I also put some stretched out coarse steel wool in the pipe just behind the baffle. The end result is a good sound and perhaps the correct back pressure.