That's the old truck rear end that was used from somewhere in the mid '50s. Sorry, I can't tell you much more than that. I haven't been into one of those before. My brother has the same rear end in his '57 truck. I think it was replaced by the truck 12 bolt around '64.
If you only turned one wheel then you only got half of the gear ratio. If you leave one wheel on the ground and turn the other wheel exactly 2 full turns and count the number of times your driveshaft turns that will be your gear ratio. If it turns just past 4 times then it's a 4.11, if it turns just past 4 1/2 times it's a 4.56... Those old trucks usually had gear ratios in the 4s.
A popular swap for those rear ends is the '67 to '69 Camaro or '68 to '79 Nova rear end. I'm pretty sure that those truck rear ends are right at 60 inches wide, which is what the Camaro and Nova rear ends are. This will also get you the smaller 5 bolt pattern for the wheels.