One axle I would not get, unless it's in great shape, for free and has your gears. The 1970 Dana44 open knuckle drum brake. It's the first year open knuckle and last year drum... kind of a one year aardvark. I had one.
Anyhow, I would go the HD44 with 8 lugs OR you can get a Dana 60. The GMs are pricey and I think scarce now. But they are truly a no brainer bolt in, sort of if you get the gears you want or the gears are on the side of the carrier break you're looking at ratios for. Off Road Design makes bushings and spacers so you can swap in a Dodge Dana 60 easily too, I think there are qualifiers on springs but you can check out their site. I've not done it but check out the 4x4 section, there are some who have. So I'm just Mr. Theory on that one!
If I were doing it, my first choice would be a 60.
What I did. I put in takeouts from Boyce equipment a few years ago. I got 16k mile "take outs" out of a CUCV. It had 4.56, I had 4.10s. It cost me $2500 for the set. Dana 60 and rear 14bolt. Boyce said they had been gone through and were drop in ready. They were, even meat on the pads.
I searched for a Dana 44 in Junkyards. I looked a little over a year and didn't really have any luck. I guess timings is everything. Once you don't need a damned axle... it will start raining axles! Anyhow, based on cost and time to go through a junkyard axle I decided to go with the more expensive option. I am now happy I did. But price was not the driving factor, though I'm not into wasting money either.
My axles are out of a 86 CUCV.
The disc brake panacea! Once in I took out the check valve from the front reservoir. The brakes worked awesome... sort of. They were touchy. So I put in the correct master prop valve and so on, for a disc drum setup. The brakes sucked! I got sick of dickering (which was pretty quick). I went back to the original master and dist block. I'm not a fan of the adjustable valves.
The touchy brakes bugged me! So I moved on to the hydroboost out of an 86 one ton diesel. I put in matching brake lines. My brakes from pedal to wheels are of 86 CUCV, along with the running gear. Makes it easier when getting parts too. But now my brakes are awesome... with no qualifiers.... I love the hydroboost and I'm glad I did it.
So, you see. There is a lot to consider. There is a lot of reading here and the internet at large. I did a brief spiel on my swap you can search on "1970 one ton axle swap" or something like that.
But if you can keep your truck drivable and you have time, you can run around and look at axles and have a truck to haul them home. Figure out what you really want and try to get it. If time is a push, then you get what you find in short order that fits the bill. I got impatient and ponied up the bucks.
Decisions Decisions! Good luck!
j