Guy I work with totalled his '98 Aurora 4.0. He has found a '97 with a blown motor. Are the motors interchangeable b/t these 2 years. He has heard that the transmissions are different b/t '96 and '97, just wanting to make sure the motors can be swapped.

Oh man.. Your so SCREWED

indyboom, maybe you should explain what you are talking about.
They all have the 4t80e transmission. The diff would be if one has the autobahn package wich is a diff. gear ratio, 3.73 I believe, the normal ratio is 3.42.
95 and most of the 96 models have obdI managment system. Not just plug and play with later models.
If they are both 97 & 98 with the same gear ratio it should work.
Good luck!