Posi upgrade help needed

I just took my 1985 (or so I was told) rear posi out with 3:23 and put in a blazer (year unknown..I assume by the look of the truck it was 87-90 5spd
4x4 3:73 posi in. I kept the disc brake setup on the trans am and just changed the ring pinion etc. NOW I am being told that before I start it, rip the pod off and pull an axle out because it changed in the years I am working on. SHIT !!!!!!!!! It turns the wheels in the air when I move the drive shaft, and I was wondering if I have a weird spline count.....there is no play in the thing when I move the axles left to right, and it went in pretty nomal...... ???? HELP !! I did this for the first time and should have asked more info. The wreckers said it would go and the factory haynes book seemed to agree
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