I've never seen the vents that others have shown. I've got vents in my corner pockets below the rear lights. I've got the 3500 ext and not sure if they configured it differently.
Sorry, I'll be drawing cold air from the garage but will push it out the front of the bed wall. Similar to your setup. I really was set on installing it under the front passenger seat but routing the intake and exhaust would seem difficult. I'll have easier access to it from the garage and I won't have to relocate the tire changing box.You won't get any appreciable warmth from the Webasto except from its outlet vent. If you draw cold air from under the bed, you will also be drawing warm air under there to replace it. Bringing warm air to a cold location may invite moisture issues. See my build blog as to how I circulate the air above the bed rather than below.
4 Grand in Batteries - sweetWorked on my wheel well covers which will support my batteries and water tank. I'm giving serious thought about putting my Webasto heater below my water tank as shown which can only help prevent my water from freezing. I'll drain the tank if I knew I'd be away from the van but just thinking ahead. This spot will also pull cold air from the garage. View attachment 61710 View attachment 61711 View attachment 61712
Looks like the spot was made or a roof vent. So, are you going to finish the job before 'de rain hits 'de roof?