I have a 98.5 24v cummins 5speed, It has a cracked block and a bad lift pump, probably bad IP, so I would like to do a 12v swap. To have a fully functioning truck, cruise, check engine light, stock gauges, etc what are my options?

1. I have read that I need a 98 pcm, but wouldn't there be more then one part number for 98 pcms? I could see there being different ones for: (auto/manual), (cruise/no cruise), (California, non cali emissions) (air conditioning/ or no a/c). Is there a part number list? Am I wrong is it much simpler?
2. What about a 97 pcm, would it not communicate with the other computers and instrument cluster?

3. Which harnesses do I need? I read I need firewall forward which is 2 separate harnesses? One is an engine harness, and the other is what the fuse box? Can I use 97 harnesses or does it have to be 98?

4. I shouldn't have to change the instrument cluster or any in cab harnesses correct?

Any help would be great because getting a complete donor vehicle is very unlikely and I will have to piece it together probably sight unseen via ebay. I would hate to by parts that aren't compatible.

I'm not sure on the PCM but from what I've read on the subject you would need the 98 12v engine harness as its different from the 94-97 engine harness.

Alright that matches what I have gathered as well. I just picked up a 12v tonight, so I am now committed.  I will probably do a write up when I get the bugs ironed out.