Just 5 days after my "roadblock" post, it looks like I have a bus! Finally was able to connect with a guy selling a bus with the exact engine/tranny combination that I wanted. It's only 35' and not 40', but I can make it work. The bus is a 1991 school bus. The body is by Ward and the engine is an International DT466 with a MT-643 transmission.
He also texted me this morning to let me know that he has a friend with an outdoor storage / work space for me to rent for $150/mo with power. I'm not too worried about it being outside in the winter since we have a bunch of nice days here in Denver even in the middle of winter that I'll be able to work inside the bus. Holy crap this might actually be happening!
I'll post some more photos this weekend when I get a hold of the bus.