Have you used Apple's scripts?  They have a web page in the Developer Connection that is supposed to do a lot of the leg work for you (swapping out the Carbon to Cocoa libraries).  I found it while looking for something completely different - which seems to be how the Apple search function works - I can never find what I am looking for.

As long as I can address more that 4GB of ram, I don't care if the GUI is 32 bit or not.  I like the new look.  It has taken a little getting used to, but I like the speed.