The frame and shells on any of the FBRVs don't add up to much
weight. It's the ammentiies and stuff you bring along that push the scales up.
Just for info -- my parents when they were still living pulled a 13 ft
Scamp all over the nation with a Renault R10 fuelled by
propane during the gas "crisis" of the mid 70's and early 80's. The Renault was supplanted by a Mazda pickup during that time.
Later they upgraded through a series of larger and larger rigs then dropped down to a 16 ft
Scamp that they pulled with a 6 cyl Toyota Cresida.
Dad always said the Scamp and the Mazda pickup, which was a 4 cyl was his favorite traveling rig.
So I think most any 6 cyl rig would pull a small FGRV just fine.