Anyone know of a trick to cross over a PN that I don't know about...like 'add a C' or 'subtract three from the number'?

This isn't in an ECM...it is in a PWM fractional HP blower motor on a '97 DeVille, but I figured I'd try to replace the bad transistors and caps before shelling out ~$250 on a new one.

Part Numbers on it are:

M(space)8699
R9634

Second one is

M 8699
R9635

So I assume the first one is the number and the second one is a date code. TIA

You might try poking around on www.digikey.com or www.newark.com

Google search might also work as well, using 'transistor cross reference'