If you want to
run VMS it's fairly available.
What would be the most appropriate version to run on a MicroVAX II or
III? Are there installation tape media images available somewhere?
Realistically? Any version you can get on a pair of good TK50's (as I
recall even V5.5 is 2 TK50 tapes). I've run V5.5 on my MicroVAX II before
turning it into a PDP-11/73. I've got V7.2 on my MicroVAX III. However, I
was able to copy the 7.2 install CD over DECnet and write it out to an RA72
and install from that, in order to setup my MVIII.
It's not the suggestion you want, but you should think about getting a
VAXstation 3100 or 4000 series machine. With those and a SCSI CD-ROM that
is capable of doing 512-byte blocks you can easily install OpenVMS, and then
remotely boot the MicroVAX II/III as a cluster node.
At least I assume you aren't lucky enough to have a Q-Bus SCSI adapter.
Zane