Move disk to new hardware?

I've got an OS X Snow Leopard Server config on a Mac Pro 1,1. I can't upgrade any further on that hardware.

However, I've got a spare MacPro 3,1 and wondered if it would be "simple" to just move the disks to the new hardware?

I thought I'd ask first just in case the disks get updated with something which means I can't go back to the old MacPro.