i can tell you what NOT to use, and that is a 73-81??) frame like the one under my truck. way too much hgt in the front for a 2 wheel drive rig. and i had to weld a pile of mounting points on it as well as remove 8 inches from the middle of the frame rails.
my stock frame was virtually flat, so new 2x4 steel wouldn't be that bad, but you would have to do welding of mounting points. maybe not that much tho.
the best part for an old truck is however, a whole new chassis. but in your case i think getting by with a new front clip would work. i don't know if your welding is up to it tho. you will be driving on two-lane highways alot. you would hate for your left front wheel to fall off in front of a semi. i imagine if you are bucks up that someone like Fatman makes a bolt in unit.
i think i am a pretty fair welder. however when i did my frame off i had a drunken ship fabricator from a local ship builder (dakota industries) as a roommate, until he went to jail.. he did all the welding on my frame. i just did all the measurements. so help is available. you would be amazed at how much free work you can get for "free beer" (or in his case, black velvet)