It is definitely possible, and once you're done with it be sure to share it with us..
I made a first search with wikipedia and consider a list of same family cpu (ex. C2D) and then cpus of the same "subfamily" (ex. "Merom").
But I think this kind of search is too generic: I know, for example, then I can replace my microprocessor T7400 with a little powerful T7600 (Apple itself offered this like option). However, I'd know a more complete list with options possibles: Apple, obviously, doesn't offer this of support or a tool to evaluate all possible options to upgrade; they are against every kind of DIY operation and they also don't support machine older than 5 years. In my situation I'm completely out of their interest!
But also in their community I tried absurdities: people say, for example that the cpu is soldered on the motherboard...... Crazy things! They say the only way to upgrade an Apple is buying a newer one (referred to cpu upgrade). These are specious falsehoods.
So I'm trying if someone knows a tool with these data.
I hope I was clear (I'm not english mother tongue
).
Bye!