Can I move hard drives from one Mac Pro to another?

I don't have a MacPro but I have owned many other model Macs and have done about half a dozen times what you would like to do, without issue. Technically an OS installation may be tailored to a specific machine, but honestly I have never encountered a problem like that, though I cannot vouch for Mac Pros. If these were radically differnet machines then yes, there might be problems, but even then as long as the OS is capable of booting a computer (so you're not taking a PPC drive and putting it into an Intel Mac) I have even taken drives out of one model and transferred to another without issue.

It should be plug and play with your drives and those machines.

If the boot process balks (for whatever reason), hold Option at start and use the Startup Manager to choose teh boot volume.

rfairley wrote:

...Can I simply shut off both machines and swap all of the drives in one for all of the drives in the other? I would keep them in the same bays in the machine I'm trading them with, but I'm unsure if I will screw something else up.

I've moved drives from a Mac Pro 1,1 to a 5,1 and they were able to boot the newer Mac, but to ensure that the OS was configured for the newer machine, I ran the appropriate combo updater once the drive was installed. If you're planning to stick with the drive rotation, doing that shouldn't hurt and might help even though the machines are of the same vintage. Note, however, that some commercial software keys in on machine specifics and/or the serial number to prevent piracy, so swapping drives can cause other problems.

The only issue you may encounter is that the build of the operating system varies from machine configuration due to the specific components/processors in different machines.

If the machine kernel panics on boot or produces 3 beeps when you power the machine on, then it'll be down to the OS be incorrect.

Never seen anything like there being a different build other than the initial install with OEM. Period. If you are worried, run Combo Update. If they had different drivers for 3rd party software or hardware, then of course add those to each to have universal OS.

That and only that.

did everything work ok? did you have any touble with apps?