You should try Option booting to see if the drive is available in the list, and has an OS X icon next to it.

You may want to check the formatting on the 7200 drives. Try Zeroing one out, and reformatting it as Mac OS Extended (Journaled). Then image over it, and try booting again. I've had issues with drives exactly how you're describing, and a Zero + Reformat = Success.

Good luck!