I mounted my MoBo in the dash... had to man-handle some extra space with my trusty Dremel to make everything fit.
As far as the power supply goes, went with the M2-ATX.
Just moved the factory radio down by the stickshift... that was so I didn't have to power up the PC every time I started up my truck. Also, since the original radio is still intact, I can still turn it up and down with the volume and play the radio and cd's on the fly. I used an auxiliary adapter that plugs into the back of the radio (into the cd changer slot).