Yep, getting whatever "extra" parts the previous owner took off is a good move. Years ago, I bought an old Triumph Tiger 750 that had been "customized". No front fender, different seat, pullback handlebars, cocktail-shaker mufflers, no turn signals, 16" rear wheel, and it burned oil and had a bad knock in the motor. Luckily, I asked about the original parts and he had them all, other than the 18" rim and handlebars, and the frame hadn't been hacked. I rebuilt the engine (pistons and rings worn badly, but the bottom end was good), and with the exception of some superbike bars and the 16" rear wheel, put it back to stock. It was a pretty bike. I rode it a few years and sold it - never did get around to replacing the rear rim.