So Eaton is out. If you want to stay with Chevrolet then it would be the Corporate 14 bolt full float.
Is this what you want? This driveline forum is for "all things driveline related Pre-'73 GM truck".
I would reformulate a new post and post it in the 73-87 trucks, HiPo or Tons 'o Funs forums.

14 axle swap (stovebolt):
https://www.stovebolt.com/ubbthreads/ubbthreads.php/topics/1249600/14-bolt-axle-swap-info.html

http://billavista.com/tech/Articles/14-Bolt_Bible/index.html
https://www.motortrend.com/how-to/129-1305-14-bolt-basics-inside-the-ultimate-junkyard-axle

If you are not good at fabrication, I would look for a kit and find a good welder.
Example, not a recommendation:
https://www.ruffstuffspecialties.com/14COMKT.html

If you go with a used 14 bolt be sure to determine the condition of the bearings (especially carrier and pinion) and ring & pinion gears.

If it was me, I would try to find a good rear axle shop near where I live.

"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."