Maybe he was trying to be cute. Posi is a trademark of Eaton, but it is a limited slip, so yeah- same thing. Or maybe he has limited slip and open rearends confused.
It may be a 3.23. They were pretty common, and with a ~26" tall tire (~235/60/15 or ~215/70/14), would put you around 3k@70mph.
An easy test to see if it is a LSD or open, is to get one tire on a slippery surface, and one on dry pavement, and floor it. If they both peel out, it is probably a LSD. If only the one on the slick stuff spins, it is likely an open, or a worn out LSD.
