I have the front end of a 72 on my 74. There are just a couple of differences one was where the bumper brackets bolts on. The holes are there where the 72 brackets need to bolt up but the inserts that the bolts thread into aren't.
I happened to have a 72 that I was parting out so my fix was to cut the inserts out of the 72 frame and weld them into the 74s.
And one bolt hole that holds the fender to the radiator support is not there, but it's in a location where you can't see it so I just drilled a hole through the support.
Other then that the front end transformation was fairly easy.
If you would like to see it click on the thread below my name. Good luck!