interchangeable

So i'm getting my first bike from my girlfriends brother. it's a 1978 suzuki gs550. he told me that the guy he got it from cut off the exhaust pipes and gave it straight pipes. so i need to replace the muffler on it. i found a used set on craigslist, but it is for the 1980-1981 model. does...

Does anybody know if I could use the plugs and ignition coils from an 83 Shadow 750 on a 500 of the same year? Doesn't seem like too good of an idea, but what do I know? So far my only other option is the wires and coils from a 93 Shadow 600. Both seem like questionable ideas at best. I'm going...