Here's some advice from a girl - make darn sure your date is going to WANT to go to the prom in your 'bolt. If the floor is nasty (or even dirty), it is going to raise heck with her dress.
Also think about how tall your truck is from the ground - your date does NOT want to be hoisting her gown up to her armpits to climb in. Getting in a truck while wearing any skirt or dress can be tough. If her gown is close-fitting, it will be very difficult if not impossible to get in or out in a lady-like manner. Most young women at Prom don't know how to handle themselves confidently in a formal situation, but they want to try - don't make it any harder.
Prom is one of the first times your date will make a substantial investment in a single-use garmet. Women make a huge deal out of the whole affair, from hair to makeup to shoes (this means her friends, mom, grandmother, neighbors, and aunts will all be involved in some way). As something that is so important to most women, the date sometimes can be forgotten and treated like an accessory (Yes, it stinks - No, it shouldn't happen, but it can).
I am NOT saying you shouldn't drive your truck. It would be really cool if you both want to do it. I am saying that you should discuss it with your date to make sure that the Prom is a good experience for both of you. HAVE FUN!