Check with your local muffler shop, though, since you want the support of the person holding the torch. I have a full custom three inch exhaust on my euro 500 SEL and it has been a fair amount of work to get the sound and torque characteristics dialed in. I was worth the work, but it's much simpler on the later cars to go with a quality aftermarket systems that fits and lasts. Sebring is OEM quality.
'76 Moto Guzzi 850 Le Mans