I was just looking on Compaq's site - it could be possible you have the PSU for the original ML350 (the model that existed a year or two ago) - which didn't have the Dual PSU option (I'm looking at the manual for such server here:
ftp://ftp.compaq.com/pub/supportinfo...201345-001.pdf)
So - it's quite possible you do have the exact same PSU as used in that box, but that server doesn't even support dual PSU's.
Compaq/HP server model numbers are broken up into 3 bits - the letters (ML, DL, BL) for the line they come from (ML - big standup servers, DL - dense rack servers, BL - blade servers), the number (350, 380, etc. - bigger numbers are more powerful CPU-wize), and the generation (nothing = G1, G2, G3, etc.) - the ML350 we have is a G3, 3rd-generation - and uses different (dual-capable) PSU's than the G1, which doesn't support dual PSU's.
Anyways - cleared up any confusion I think, pictures still coming when I can get the camera here. (and if ya have other questions about Compaq servers I'm happy to answer 'em if I can, I work with the stuff every day here - or other pictures if you want, we have DL360's, DL380's, DL580's, ML350's, all across a mix of G1 to G3)