SMB should have the build specs. You may want to call them.
Did you get a copy of the build plan layout - it may show it.
If RV style I think the A/C replaces the vent on some RV's.
1995 E250 2x SMB White Contempo Top Custom SMB Interior 5.8L (351) 69K miles
Added Propane Tank & Propex HS2800/20 Gal Fresh inside/20 gal gray underneath behind axle
2.8K Onan/Porti Potti Shower Area/110V Digital Oil filled Electric Radiator Heater/Dynaglo for backup
Hankook Dynapro ATs 225/75-16 LRE
New to me 10/2008 - 2nd owner