I think the Rek-O-Cut that Bastlnut pointed out will be your best bet. Frankly, that is the only one I've seen that has the proper setting for 78's. If you are archiving your treasures, do it properly.
And yes, they will sound different with the RIAA compensation. There is at least one computer program to correct for such deviations, but this won't help if you just want to listen to other old 78's.