It's my understanding that a "B" is a van that has a modified interior to accommodate a bed, kit, bath....
A "B+" is an extended "B" and has a small storage space over the driver/pass area....
A "C" is a small truck cab and frame (think F350 or F450) that has a motor home built on the frame (where the truck bed usually went) and usually has a bed over the cab. It can come in a multitude of different lengths and always has a gas engine.
A "C+" is the same as a "C" but will have a diesel engine and a more heavy duty frame. Some even come on a large truck frame (like a Freightliner) and can be up to 40' long but will still have the cab of a truck .
An "A" is a complete motor home built on a truck type frame. The driver's area is part of the living room (both chairs can be rotated 180 degrees). It can be either a gas engine (up front) or diesel (in the rear) and can range from 28' to 45'.
Typically the $$ range will be from a low on a "B" to a high on an "A" with a "C" in the middle.
Hope this helps
