At 6'6'' I needed all the extra room also,I found that one built on a Chevy Chassis was so much better than the ones built on a Ford Chassis.
Here is what I found.
Length The Chevy is 9 inches longer.
But the real story is the interior.
The area from the Dog House to the kick panel,the floor board where your feet are.
The Chevy is 18 inches wide and mostly flat.
The Ford is 15 inches wide but has a 2 inch rise that is 5 inches wide leaving only 10 inches of flat floor.
With the seat pushed back as far as it goes on both the Ford And Chevy. Both having Stock Factory seats
I found.
Foot well depth to front of seat. Chevy 31 inches Ford 27 inches
Seat back to steering wheel. Chevy 26 inches Ford 23 inches
Front of seat to Dash. Chevy 29 inches Ford 23 inches 6" More leg room!
Dog House width,measured at dash Chevy 15 inches Ford 23 inches 4 inches less knee room for passenger and driver.
Dog House depth into cab from dash Chevy 8 inches Ford 11 inches
There are quite a few Class C or C-(notice that I did not say the fictional Class B+) that are built on a Chevy Chassis
One Example is The
Leisure Libero that may fit your needs.