Safely is the key word in your question. Pulling a trailer with a fifth wheel or goose neck will be much more stable then a bumper hitch trailer of the same weight. As for pounds a 7000 lb fifth wheel of goose neck is enough on roads that aren't to hilly, but will work a 350 engine pretty hard in mountains. Also can do in the tranny. A 3/4 ton pickup is much more stable with the same trailer and same motor.