Hi guys and gals? newbie question here

I have a 68 dart GT that I had started on a few years ago and then became ill and could not do anything to it. Hoping to get going when funds are avalible. When I got it it had the complete K missing rear axle hanging by one spring spare tire sump rusted out and no gas tank.The interior was complete console and all despite the rats. I bought a 73 4 door with 318 and a bad tranny and bred the two together along with new front end parts poly bushings and all. Drove it around a bit with a gas jug under the hood for fuel to try it out, you know one of those cant wait things.
But it hasn't rolled in about 6 years. Plan on some sort of street toy project with rear spring relocation and moving tubs to frame while repairing trunk floor and extensions. Hoped to need traction some day 400 + HP possibly nitros ? Sticking with the 318 for a while but also own a 360 and a 400 both need rebuilt. Got a great 440 but was hoping to retain power steering.
Looking for opinions on rear axles. I own a dana 60 that looks to be from a ford van and a 9 inch from a full size bronco. Both are open diff. Question is which should I have modded narrow, posi, axles to use or go to something else, Don't want to peve off the purists with the f word sorry. What would be the most cost effective poor boy you know.