If you get a long bed truck and a camper around 9' long, you'll be able to tow most anything without a hitch extension.
Some campers like AF don't hang down at all below bed height. That helps as well.
For comparison, I have a short bed Dodge with the AF camper in my sig. it sticks out almost 3' beyond the bed and I can tow my Mastercraft with a 12" hitch extension. Barely. If I have to jack knife the trailer close to 90 deg I need a longer extension.
Meaning you can handle about a foot of overhang without a hitch extension.
Exact fit depends on the particular camper and trailer configuration.