Pillaging 1981 kz1000P for kz1000J Parts

Greetings all.
I've been considering taking my Kz1000J back to stock exhaust, and have a possible same year P model I am thinking of buying for parts. Anybody here have quick ideas as to what is compatible?
Other parts compatible as well?
Should I attempt to find a factory parts catalog or is there something I should reference online?
Any expertise shared would be appreciated.
Feel free to tell me if this idea seems foolish.

I'm not sure what police parts will fit but you can go to www.kawasaki.com and look on the left side for "Owners Information" and select "Parts Diagrams". There is a reference that will tell you every model a particular part was used on.

Thank you. I will cross my fingers and start reading.
If this works out, I hope to end up with a pair of interchangeable bikes to play with, so I can try all the risky maneuvres on the cheap one.

Hmm.. doesnt look like a lot of things interchange, at least not without modification, and it seems at first glance that the 82 police bikes are a closer cousin to the 81 J models.
Also , the owner doesn't have a title... and says "It came from a different city... if you buy the bike I'll tell you where it came from...." :huh:

I THINK the police models didnt switch to the "j" style motors till 82

Read this:http://aperaceparts.com/tech/techkz1000.html