I think I have a PCM going bad, and want to know what options I have for swapping out a different one. Car is a 98 L67 and the only spare PCM I have is a 97 L36, I assume the spare PCM I have wont work, but my real question is what will?

You can go in and change the tune on the L36 tune to match your L67 tune and it should work.

Okay I was just worried about any potential hardware differences that would stop the 99 pcm from working.

Oh wait, different years, I misread that. Might have a problem, but I can't say for sure. Not sure if all 97s had this, but the Bonneville has timing reading as negative, not sure if that will effect anything. Looking again, you say you have a 98, but have a spare 97, but then mention a 99 PCM. OK, now I'm confuseld.

As far as pcm'* go.
94-94 interchange
96-97 interchange
98-02 interchange

The only differences beyond the years that interchange is the models and programming on the pcms.

If you need one and have a certain year/model etc that you need programmed, I should have a 98-02 pcm here and can program to your needs.

Sweet thanks Bill I have a 98 PCM I am almost sure is dieing on me, and a 99 PCM that is good, so I will try to swap them out tonight.