The Stovebolt Site Forums The Shop Area Engine Shop positrac rear-How to tell?

I have a 57 GMC 3/4 ton and I'm hoping to do a ring and pinion swap. Called Patricks and they were very helpful. I told them I had a Spicer 60 rear with 4.56. I was under the impression that it was positrac as I thought I read somewhere that if you jack up the rear and turn one wheel the other will turn in the opposite direction. Do I remember wrong? The guy at Patricks said that posi will both turn the same direction. Also, to confirm the existing ratio I counted revs of axle with both wheels off the ground. Right at 2.25 per 1 wheel revolution. 2.25 x 2 wheels = 4.5 (close) Does that sound right or am I way off on calculation procedure? He said to try with only one side up so I did. 2.25 and wheel would only turn in reverse. Does this sound correct?
Any help to clarify my fuzzy thinking would be greatly appreciated.
Also, He said the carrier would have to be changed to accomodate the gear swap (3.54). Would a less drastic gear change make a difference in the carrier change? Sorry for the long post. Thanks again.