Tell me, how do I discern a regular 10 bolt rear end from a 10 bolt posi by appearance? Also, with the rear wheels off the ground, am I correct in assuming that, when you spin one of the tires, with a regular rear end, the wheels will spin in opposite directions, and with a posi, they will both spin in the same direction? Thanks for anyones help.

If you have the car in gear, the wheels won't spin at all with a full posi. A limited slip posi. will act like an open rear when you spin one wheel by hand.

Visually I dont think there is a difference, however,,,if its a stock rear there should be a little metal tag bolted onto one of the rear cover bolts.

Wheels should spin in the same direction I believe if its a posi.

There is no difference in the way that they look on the outside. Spinning the wheels will tell you nothing. I have seen too many posi rear ends with worn clutches that will spin the wheels in opposite directions like a standard rear end. I have also seen standard rear ends that will sping both wheels in the same direction because the differential was damaged from doing one wheel burnouts, or an axle tube was bent. There is ONLY ONE WAY to be sure. Remove the cover and look inside. If you don't then you will not know what you are getting.

I didn't have a means to remove the cover before I bought it, and now its in my back yard on blocks, so needless to say, the cover is coming off. Replacing differential oil is the first thing I do anyway to a newly purchased old car. Thank you for the replies.