Buy the parts? I'm thinking it's as simple as getting the bumper, taillights, valance, maybe the qtr extensions, and hardware...but I've never personally done it.
Do you have, or are you thinkin about buying a '74 you found?
I have done this to my 74 and you will also find a few more on this web site that has did the same.You need the complete rear panel-braces-lower valance-bumper brackets -bumper-quarter extensions and tail lights.Not for the mild at heart tons of work.