1966 Valiant Signet Power steering pump

Welcome to FABO! I assume these are both power steering cars and this is not a conversion. A lot will depend on which pumps you're working with. If they're both the Federal (TRW, Thompson) type you'll have to swap the reservoirs or change the return line fitting on the box. If you're going to put a '68 Saginaw in place of a '66 Federal, you'll need the brackets and hoses with it, probably a new belt, and again change the fitting.