part number history?

Greetings,

I have two 912UL engines, one is old (4405028), and the other is REALLY old (4005342).  If I'm looking for used parts, I often find parts with a number I can't find anywhere.  The parts manual only seems to list the current number, but that has probably changed a half dozen times at least over the years.  Is there anywhere that lists the history of part number for a particular part?  Also, can I assume any part listed in the current parts manual will fit my ancient engine, assuming there isn't a note that gives a SN range?

Thanks,

Rusty