Try this site. They have lots of parts for old bikes. Be prepared for some sticker shock. EDIT: I just looked. They have them. About $140 each. Ouch.
You can run straight pipes if they are allowed where you live. Be prepared for it to be loud. Be courtious in residential areas. Try to keep it as quiet as possible after hours. His will help keep the neighbors off your case
Be prepared to go with larger jets in the carburetors. If you don't, expect a noticable loss of power and fuel economy. It can run hot. You risk burning valves or pistons. So a carburetor rejet is a must.
