Warm her first with the idea of riding in it at the parades. Then tell the wife how deprived you were as a kid and that this truck would make up for how you feel so depressed when you think about it. Then tell her you think you might have to go see a shrink to help you get over your childhood and in the long run this truck would be cheaper. If that still doesn't work then remind her how much time it would take out of schedules and gas costs while going to the shrink.
LOL!! Well, does it sound good enough to work?