Is anybody even going to notice? I have a few older bikes (mostly stuff I used to ride that wasn't worth enough to bother selling it when I bought new bikes), and i enjoy them as they are. If the older bike had steel rims, I'd replace them for sure, but I think by the '80s almost everybody had gone to alloy.
Two other points: Will new Bontragers last (I don't know anything about them, but at 240 pounds I often have trouble with light wheels), and can you make the swap without new brakes? I have an old Trek I can switch between 27 and 700 wheels just by moving the brake pads, but that's not common.