I'm not sure you'll be able to even run V5.5-4Hx (I think that's the high mark for V5.5 and I'm not sure what the 'x' was), and I'm pretty sure you can't run plain V5.5. You might need to go with V6.0 in order to have VMS support your hardware. If you can get someone to build you tapes, I'd recommend getting V7.2 or V7.3 instead of earlier versions if you can, as all the doc's are available online.