[454_72_4X4]

I'd use your original frame and put the 4x4 front axle under it. Just about any D44 or Corp 10 bolt will work.
It'd probably be easier if you can find some 67-72 front spring hangers/shackles, but 73-87 parts would work also.
Like mentioned above the high hump floor is better.
Is your truck a coil spring rear?
I've always wanted to put a 3/4 ton coil spring suspension under my 72 and then mount the rearend under the control arms to make it 4x4 height, (or closer to the right height anyway).