As for the Letter Designation of Dodge Based MotorHomes, here is what the Factory Official Dodge Service Manual says : B300 can be a Van, a "Wagon", a "Maxi-Van",or a Maxi-Wagon".
MB300 is a "Front Section", which is the Incomplete "Van Chassis" that is purchased by the Varied Coach Builders, from which they produce the finished Class C Motorhome.
A CB300 is a Category for Chassis that are destined to become the "Ryder" or "U-Haul" TYPE of Hauling Truck with a rectangular "Box".
(In Later Years, the "300" is Re-named to be "350".)
