How interchangable are the keyboards for the non-unibody 17" MPB's?

I have the MBP Core2Duo model A1212, but the keyboard and trackpad are awful. Could I just replace the whole top of the comp if I find another non-unibody 17" MBP?

How interchangable are just the keyboards or just the trackpads between the various models of 17" non-unibody MBP's?