This will probably be an unpopular thing to say, but I think that the buyer of a trailer is the one who should be responsible for deciding if their truck can handle it. The trailer salesman ought not say anything at all about what vehicle can pull it - just give the manufacturer's weight of the trailer and let the buyer go from there. Before you buy a trailer, go borrow or rent one and see how your truck handles it. See how well it accelerates. Do some hard braking and see how fast the tuck will stop it. Go up and down some hills. A person who's done some towing will be able to tell how a truck will perform. Somebody will say, "But you won't be able to see how it does in the mountains." If it feels sluggish on the straight and flat, it won't be able to handle the mountains.