Nothing comes close to 7’. Parkliner
and Lil Snoozy
are among the tallest at around 6’5”. Both have transverse queen beds. The Snoozy’s rear entry layout would adapt well to a truck mount.
Most are around 6’ to 6’2”. A few are less. With just about any travel trailer you’ll have under-hanging plumbing and holding tanks to re-engineer.
Do you have budget and/or length constraints?