I just came across this... It looks like a great clean solution for adding a Sata3 drive to a Mac Pro... Bootable on EFI64 machines...
http://www.apricorn.com/products/desktop-ssd-hdd-upgrade-kits/velocity-solo-mac.html
http://www.apricorn.com/products/desktop-ssd-hdd-upgrade-kits/velocity-solo-mac.html