for one, your coils being BLUE is a REALLY BIG CLUE. and these 4x4's were actually quite low from the factory..but anyways moving on.
okay, here is what i would do if i were in your situation. now pay attention! i have owned over 20 73-79 ford trucks and broncos, both 2wd and 4wd. now the first question we have to awnser is what size tires do you want to run? that will dictate as to what coils you buy.
i would find a 78-79 3/4 ton front axle and take the outers off of it and put them on your half ton axle, swap the gears from the 3/4 ton into your half ton and then swap in a dana 60 rear, that way you can awnser questions in the parking lot about your coil sprung 3/4 ton
6'' coils with no body lift would run 35's...i wouldnt go any bigger cuz then you run into problems with the law, it turns into a toy and you sell it for a fraction of what you got into it, keeping it on 35's means you can still use it.. and as a general rule of them...i hate body lifts...on the other hand you already have a lift...you could just hack the fenders..