I'm using a 2007 Nissan Frontier with a 4 cylinder engine & 5 speed manual transmission. The factory recommended specs are:
Truck weight 3,675# (Leer camper shell add 175#, total of 3,850# as it sits now)
Gross trailer weight 3,500#
Tongue weight max 350#
Combined gross weight 7,936#
Maximum frontal area 60 square feet
Engine is 152 hp @ 5200 rpm, 171 ft. # @ 4,400 rpm, currently around town mileage is 22-23 in the winter, 20 summer (AC running all the time)