It won't directly bolt up, no.
I did, however, take an '81+ bumper from a CUCV and put it on a '74 K5 with some square tubing inside on the top bolt holes as a spacer. I seem to recall 1" or 1.25" being required for it to align more-or-less straight.
But, as mentioned, the '73-80 bumpers/frames don't directly interchange with '81+.
-- A