What about if, after swapping the drive, you started up immediately from the new MBP install disk, and did an archive and install? Wouldn't that install everything necessary for the new MBP to run while preserving everything from the not-so-old 7200 rpm HD?
You could then buy an external case (either a usb/firewire case or a usb/esata case along with an esata expresscard) and clone the 7200 rpm HD onto the original MBP HD in the external case.