What do you think about this situation?

In my opinion, when the purchaser stated his concern it was not addressed, he was specific, when the vehicle was ordered and they found the 3.1L was not on the list of engines available the purchaser should have been contacted and notified before the order was completed. That is when you need to resolve the conflict not when the car gets there, so the dealer was at fault here and should refund the deposit, because the contract had been breached upon ordering the wrong engine. Besides that the dealer can stock and resell that car as new as long as the person never took delivery. The funny part os this scenario is the 3.8L gets better gas mileage than the 3.1L. The salesman needs to know what he is selling especially when dealing with specific orders as this. The dealer loses nothing but this sale and they need inventory on the lot to sell anyways