70s frame under 80s truck

[AMS28]

I'm trying to put a 1970s frame under my 1987 V10, and I have an 80s front bumper. What do I have to do to get the bumper to fit, as well as other miscellaneous differences between years?

 

[nvrenuf]

Body bushings are different and need to fit the frame, the bracket holes are different.

The forward end of the 73-80 frame is closed whereas the 81+ is open and uses a bracket for the bumper. I’d imagine you could cut the end to match the later frame but I’ve never done it.