So are most Class 8 conversions a Class C or are they Class A's?
-By definition, most Class 8 conversions are Class C motorhomes.
Where do the Class 8 conversions fall in regards to their classification as a Class "A", "C"...?
-See above.
Motorhome size has nothing to do with classification?
-No. Configuration determines classification
Is this classification clear or are there gray areas?
-Well, either a chassis starts with a cab or it does not. Anything gray about that?
What Class A motorhomes would start as a Chassis with no cab?
-All of them. They start as a bare chassis with a temporary seat, steering column, control pedals, and maybe a dashboard, but NO cab structure
Are there advantages/disadvantages of having one over the other?
-Depends on whether you want a truck cab around you, or the same structure as most motorhomes(This ought to be a no-brainer)