Ah, I see now. I wasn't aware of the MDD 2003.

It looks like that's probably got the board I need.

http://lowendmac.com/ppc/mdd-power-mac-g4-1.25-ghz.html

Unlike the original MDD models which all had dual G4s, it has only the single 1.25 ghz chip. My FW800 has a single 1 ghz chip. I would suspect they would be the best match? Or should I find a board that has the same 133 bus instead of a 167 bus?

Thoughts?