OMG!!! Thank you friends for my education.

Dealer was only interested in making a sale and clueless to the other numbers. What the OP could've done if possible and really "P" the dealer off was to test drive "X" truck, go to a scale and weigh it w/ salesman in tow. THEN add in weight of passengers to get to what's left for capacity. I went to a dealer once and before walking in I could see the sales folks straightening up their ties, donning sportcoats etc. I walked in and was asked if I could be helped. Told them yes and asked them one simple question. tell me sir/madam, which do you yourself sell more of cars or trucks? Cars was answered. Good then, point me to someone who sells trucks. No more puffy chests and ties shriveled up.

Good for you OP and sticking to your guns. perhaps check w/ a dealer who has fleet trucks/dep't.