Is the rust creating a problem (other then in the eyes of the OP)? Are the pivots frozen? If not then just clean and lube. Shimano really isn't in the business of making repair parts for a $15 frt. der. As the rear gear count goes up the frt der cages get narrower so at some point there's a lot of chain rub when used on a lower count system. Shimano will say that their stuff only works as a complete system with all parts matched in gear count (and road or ATB spec). Some mix and match can work well but you're on your own to find out exactly how much. Of course it's cheaper to stick with just replacing the frt der with kind then replacing more parts. BTW there's nothing antique about this der. Andy.