[lizziemeister'sV6]

The axle he is describting sounds to me like a Chevrolet full size passenger car from the mid to later 1960's. Most were open rear-ends unless they it ordered along with a high performance engine which then would be positraction/limited slip versions. 12 bolt posi could be ordered in full-size , mid-size and compact cars with higher horsepower engines. The GMC rear-ends are unlike the Chevrolet versions in the way the axles are secured.