I don't know if this will help with your a/c question, but my biggar's a/c opening is 33 inches from the centre of my front vent to the centre of rear/c vent , right where the
fridge sit's, there might be an vent hole already up there and they just panelled over as a/c wasn't called for , the power wires from what i could see run towards the
fridge an down to the power centre, Removed my air conditioner and capped off the wiring , put in a maxx fan.