Hello micjmac, welcome to Seven Forums!
If you wanted to have them boot independently of each other you would have to disconnect one HDD and do a
startup repair to the other HDD/OS as many as
3 separate times with system restarts
between the repairs to write the Windows boot files to that OS; then you would need to do the same process to the second HDD/OS, then you could use the one time boot menu to choose which OS / HDD you wanted to boot at startup.
I have used the tutorial that Dwarf posted and it's very effective to re-name them at the Windows startup boot menu; here's a tip: do the OS you're in so you can use the {current} to your advantage, then boot to the other and do that one, you'll see what I mean.