Hi Tango - joined this thread late and I've been flicking through the posts watching (and enjoying) your progress. I've been contemplating a conversion of my own based on a truck chassis and I was delighted to find a bunch of fellow minded people, although mine will be a lot smaller than most of the bus conversions here, but at about 21 feet she'll be about the same size as yours. Seeing others bucking the trend and creating their own vehicles is inspiring. Appreciate you sharing your experiences.
I saw at the start of the thread that you were going to change the small block for a diesel, and I see that you went with the 4BT. I'm looking at a diesel swap (I currently have a 352 Ford V8 that returns abysmal gas mileage barely into double digits) and I'd looked at the Cummins - both the 4 and 6 cylinder motors. Beautiful engines and extremely reliable, but for anyone considering a swap the Isuzu four cylinder diesel is also worth checking out. It apparently has an overly complicated electronic transmission, but GM, Ford and Allison transmissions fit with a conversion kit and it's supposedly an almost bulletproof motor that returns great MPG. Lots of them languishing in Isuzu and GM badged box vans and normally aspirated and turbocharged versions are available depending on your needs. Hope you don't mind me dropping this into your thread - I know it's a bit late for your project, but thought I'd throw that out there for someone else thinking of going diesel.
BTW, I absolutely love the look of your bus - classic lines and probably nothing else like it on the road. Can't beat that