Planning Build! Need inside dimensions of 6 window

[NickandNarlie]

Hey Y'all! I'm new to the skoolie world and I am about to purchase a 6 window Ford E350 skoolie. I'm wondering if anyone knows the buildable space length and width of this type of bus. I'm trying to come up with a 3D model for my build before I start and it's tough without knowing the size.

 

[Jolly Roger bus 223]

need to share bus body manufacturer to get better responses.