Lookin’ for a newer model

I'd sort of like to BE the girl, IN the car. And we'd both have rustproofing.
My stomach has continued to bother me on and off for the last few weeks, and today a friend asked how I was doing.
HIM: How’re you? And your tummy?
ME: I’d like to trade this body in. I can do 10% down and $399 a month for a new model.
HIM: Yeah, but for $399 a month you can only get B-cups. C-cups cost an extra $50 a month. Especially if you want rustproofing.
My question now: What part needs rustproofing?!

