1976 K20 - Factory front Posi?

['63GENIII]

Hey all,

Tried searching this and Im also in a bit of a rush. Im looking into finding another front axle (Dana 44) for the '63 as I just found out yesterday while tearing it apart that one of my knuckles is hosed beyond repair.

I found an axle on CL thats 2 hours away which I can get on my day off tomorrow. Its out of a '76 K20 thats being parted. Same ratio, hub locks, rotors etc. The thing thats throwing me off though (and it's not a deal killer either) is that the guy is saying its a factory POSI front axle. He says its stated on the SPID sheet in the glove box.

I know I live under a rock, but was factory front POSI available or common from the factory in the square body trucks back then?

Any info is appreciated! Gonna try to get out there tomorrow to grab this thing.