Luckily we were able to connect with a local company in Calgary; Fleet Products/KBR Brakes, who were able to quickly identify the correct replacement and had one in stock! This company has an American counterpart as well; Power Brake Sales. This website was super helpful in trouble shooting and installation: http://dave78chieftain.com/MidlandRoss.html In addition our vintage Dodge Trucks resource book was quite helpful, a few excerpts are below:
The new booster is a Midland Ross C-462, installed, all nicely refurbished and painted. We also found a new booster air cleaner 1/2 inch (part number 2503225).