I agree with Brian, the most important thing is that you a happy with what you have :)
Unless you are a collector or dealer it really isnt important that all parts are orignal... Parts wear out over time and are replaced with what is avaliable... Also, motorcyclists were just as much into customising thier ride back then as we are now :)
At the end of the day, these 650's arnt worth a heck of a lot even in original condition so have fun with what you have, and dont be afraid to change it up some more to make it a bike you are truely happy with :)
Have fun with it! :)