As others have said, the length and weight of 5ers are not necessarily proportional. Some 5ers are built very heavy and some of equal length are built much lighter. And some 5ers of equal length, and even of the same manufacturer, can vary several hundred pounds of pin weight depending on the particular floor plan.
Check your truck payload and tow rating. Newer trucks have greater weight ratings than those of just a few years ago. I tow a 34'-8" 5er (according to manufacturer specs) with my F350 CC LB SRW. Tows very well and am within my weight ratings.
