MKIII output tranny mounting holes - chassis dims needed

[Shannon Parks]

I'm planning to mount a new power supply board (new diytube product) on the A431 output mounting screws. This will be handy in upgrades as that area is basically clear. Looking at Triode's datasheet, it looks like around 3.00" by 3.375", but I realize the actual mounting holes could be a 1/16" off or so. Does anyone have a chassis handy and a mechanist's ruler to give me an accurate measurement?