I googled Ultra's service manual. Looks like it uses +12v, -12v, +5v, +3.3v and +3.0v, so would need to generate that last one separately.
Anyway, there are people on that project's Discord channel installing this on Sparcstations. I haven't used the PSU myself, just the USB4VC project (to connect USB devices to PS2, gameport etc) from same creator.