I cant find a single 88-98 bumper shaped like that one88-98 style bumper . not a bolt on at all . and fyi 88-up body style the frames bow out after the cab and get wider unlike out 34" frame width .
sorry 99-06 trucks . and most were crap and rusted apart bad . 
I don't think they are the same ones,
I think you will have to modify the top of the truck bumper to clear the hinges and spring of the K5 gate.Somebody remind me why you wouldn't just use the 73-87(91) truck bumper? It has a step and the frame width is correct. I seem to remember there is a small fitment issue, just don't remember what it is.