Ring and Pinion gear change question

[pvienneau]

Anyone know of any reason not to rebuild a third member with 3:55 gear and pinion out of a parts truck AD rear end and then use it in another truck? This way I can do all the work with minimum time running truck is off the road. Both are 1949 AD Pick up trucks. I guess question is are the rear end parts all the same with the exception of the left and right bearings which are machined at time of trucks birth.