Life is short, and we seem to get bogged down with "wants" or "wishes".
Why beat yourself up looking for rare stuff that you may never find?
What is the truck? 2wd or 4x4? What wheel offsets? What I would do for the 5 on 5" is just get a late 70s to late 80s chev/gmc 1/2 ton 2wd rear. Yes, it is of "throw away" quality compared to a 44, but so easy to find a good donor with a good ratio. Those rears are about 1.5" wider than the 69-and-older rears, but that width really helps fill in the rear tire wells.
a 4wd rear will work from 70 up, but you need to swap in the 2wd 5 lug axles from a 71-up.