Owning both a Northern-Lite truck camper and now a Class B+ camper I can testify to my 11' high garage door opening.
Back in 2003 when we purchased our truck camp we quickly found that it was too high for the 11' door, so after some research I found that if I swapped the roof AC unit for a low profile Polar Cub AC I could just clear my door and run my AC with a Honda EU2000 generator which as you know is a great perk!!:)
So when we traded for our current class B+ camper we wanted a rig low enough to store in our existing garage.
Our 2006 Trail Lite Model 251 with the Chevy 14K chassis is 10' 5" high with the standard roof AC and I have 6' 10" head room inside the living area too.
Good Luck in finding the rig that meets your needs.