65dynamic

I currently have the stock 2.93 open diff in my 65 dynamic 88. I am wanting to upgrade to the posi 3.08. I found a 65 olds 98 and am wondering how to identify what rear end it has. Can i tell by the vin, ac/non ac, or should i ask the owner to get under the car and try to locate the two letter code on the tube?
Also if it has the rear end i'm looking for, will the 98 rear end bolt right up to the 88? Or would i be just switching out the gears and axles?

Thanks

Oldsmaniac

I am pretty sure the rears are the same but possibly the 98 had larger brake components within the drum. The rear is a Pontiac type with the 10 bolt cover and hourglass shape to the cover. Hopefully someone can support this...