The only factory swb ¾ 4x4’s that I know of are Dodges of the 60’s and early 70’s.
No need to do a frame swap on this era of GM. Just swap in a rear 14 bolt 10.5 axle and swap on front 8 lug brake rotors and backing plates like I did to mine. Then I guess you could call it a swb K20.
The front dana 44 axle is the same on 1/2 tons and 3/4 tons other than the outers. There really are no major differences between a ½ ton and ¾ frame rails in those days either....just leaf spring packs and beefer axles.
People have been swapping in 14 bolts and 8 lug front brake rotors for years on short beds. Go over to CK5 or any offroad forum and there will be million posts on it. The reason why all the offroads are doing it is the small 12 and 10 bolt axles are way too weak for sever off road use when spinning big meats, locking differentials, etc. That is why I swapped in the ¾ stuff.