I founs this in the trash the other day. If anyone can date the serial number, it's 9B05519, located on the front of the lower headtube lug. I'm guessing late 80's, but I really have no idea. The tubing is Tange Infinity MTB, double-butted. Anyway, it came with Suntour XCM derailleurs and Accushift thumb shifters, and I don't have any experience with either...are they decent enough that I should keep them on there? The bike is down to the frame right now for an overhaul, and I don't want to build it back up with something I'm going to want to take off later. Also, the rear wheel has a 13-30 6speed freewheel, and the derailleur is a long cage. Does anyone know if I could use a 14-34 "Mega Range" 7speed from a newer Giant bike? This is going to be the trailer hauler(aka "tow truck"), so it would be nice to have the larger gear on the back.