There's "frame stretch" that extends the wheelbase. You can look in the door jamb find two labels. There'll be one from say Ford noting the wheelbase that Ford built the chassis at. Then another from say Jayco saying what wheelbase they built the coach at. The difference is the frame stretch. On ours, 158" and 218" respectively, meaning the wheelbase was stretched by 60", a full five feet. And probably another label saying who stretched it, Mor Ryde for example.
Look at the MORE LATER, gotta run