- Ground - black
- 5V - red
- 12V - yellow
This is all you need for the floppy power connector, so we're in luck.
Solder some wires to the underside of the power supply PCB.
And feed it out through some vents in the box. I salvaged the floppy power connector from a spare ATX power supply I had laying around my (currently very chaotic, post-move) apartment.