can work,
for 80 and older frames you gotta cut the front frame rails(horns) off at an angle about 45 degrees or so in order to bolt up 81-87 bumper on
chris uhmm forgot his name in arkansas i believe? did this and has pics, the factory simply just vut off the horns at an angle and redesigned brackets and design of the bumpers
the end sof the bumpers turn back sharp with the new 81 up fenders deisgn
rears all same no biggie, can use form at least 64 on up through at least 87, minor spacer might be needed like 1/8" possibly in some cases.,
no biggie
at least on pickups anyways
dunno k5's though
i know more mods were done to chassis in 77 on those
good luck