it may be the same though, its a third member that fits into the rear axle from the front like a ford 9 inch. would the car and truck have used the same carrier?
Not mine but there is a POSI on KIJIJI http://ontario.kijiji.ca/c-cars-vehicles-auto-parts-tires-transmission-drive-train-Chevrolet-4-11-Posi-rearend-W0QQAdIdZ571013279
1961 Chevrolet 4:11 POSI differential pig fits 1958-64 chevy impala/corvette used but appears original, tight, GM gears_ posi. ratio to low for my application_best offer.