I have legacy outback automatic year 2000. Need to know if I replace the gear box does it have to be the same serial numbers on the box. Brought a gear box off ebay it was a 1998 one and was told this would be ok, after taking the box out, I found that the bell housing was different, the number of holes differed from the box that I had taken out.

 

Not sure about autos but the manuals from 99> have more bolts than previous years.
Manual boxes are all interchangable