Where to cut hole for fan vent in 91 GMC Vandura?

[Calibound]

Anyone have dimensions where to cut 14" square for maxxair fan vent in 91 Vandura?

 

[Wanderer]

You'll want to avoid the supports...

I have to yank out the upper air system before I cut into the top of my van....I'd do it in the back, but I'm not too sure I want it there.

 

[MrNoodly]

If the headliner is in place, or the ceiling has been paneled, you'll need to remove them enough to see where the supporting ribs are. If you have some kind of conversion van with a load of stuff mounted to the ceiling, good luck with that.

 

[highdesertranger]

doesn't a 91 Vandura have the flat spot in the roof for mounting a vent? highdesertranger