Front diff question
 

On a '77 K10 would the original front diff be limited slip or posi?

Re: Front diff question
 

It seems unlikely that this is or was offered since it would make the truck skittish.
If you mean limited slip vs posi as far as I know they're the same thing. "Positraction, or positive-traction rear end, is a General Motors brand name for a limited-slip differential (LSD)."

Re: Front diff question
 

The differential would be 'open', no clutches or mechanical way to engage or lock both wheels.