Here is a good reference site from fabo tech section
http://www.forabodiesonly.com/mopar/showthread.php?t=12985
The 8-1/4 rear is pretty good for a car with 318 or 360 with less than 400 HP. If it doesn't have sure-grip, the gears and posi units from almost any year 8-1/4 will work including from Dakota pickups. Good luck and enjoy your ride.