So your '88 must be a crewcab, or a cab-n-chassis (was originally made without a bed) to be the old body style.
In any event, the 1-ton frames are a bit different. Whether this affects plow fitment, however, is another issue.
The frame is taller and thicker on a 1-ton than on the 1/2's and 3/4's. I forget the details, but it's like an inch or two taller. Additionally, the frame rails are closer together -- at least in the back.
In the front, I believe the two frame types are identical, or at least similar. I know that the winch bumper from my '74 K5 fit onto my '74 one-ton dually, so the frame rails are at least the same outer width.
(NB: 73-80 frames/bumpers are different from 81+, but this won't affect you since yours are both '81+.)
I would take your buddy up on it, unless someone here posts up with specifics as to why they wouldn't work. I suppose it'll depend on how they mount to the frame; again, the frame on your dually will be taller than the donor trucks's. As long as the plates attach to the sides and/or top, i.e. not to the top AND bottom, you should be okay. You may have to do a little drilling or prying with a crowbar and swearing ... but I've often had to do that mounting bumpers even when they ARE an "exact" fit
-- A