I know this is from a bit ago, but I did want to chime in that I do own 2 of the PCI adaptor boards for the Stage II rockets. I got them both from an ex-Radius engineer several years ago He said they came out of the Radius fileserver pre-press machine that used 12 Rockets stage II in it. I can never remember the name of that project. But these were usually used for the Fiber networking cards he said. I have two of the base PCI addons, bu but only 1 of the PCI slot attachment angle part. The pictures posted above are exactly what I have but minus the fiber card attached to it.
UPDATE: I remembered what it was called. Skylab was the prototype project for a 14 Stage II Rocket system which Radius was rumored to have made 3 machines. My PCI addons came out of one of them I was told at the time. I really wish I still had the emails etc from the guy on ebay I bought them from. I was going to to bring my setup to VCFSW this year but ran out of time. I have a Mac II with a Daystar Turbo 040 on the main board setup, but then have 4 radius rockets stage II and a YARC NuSprint card installed to run Infini-D multinode rendering. when they are all cranking away it pulls 450 watts from the wall... 200 over what the PS is rated for. oops.