Aside from the size and body type, everything. It's kinda scary. Music, family situation, relationship with my father, my automotive background ( I still do body work and used to work as a mech in HS.), hell even my mom... YOU'RE IN MY LIFE...
Anywho, if his taste in cars is anything like mine, he's going to have a huge soft spot for the pre-suez oil crisis cars but at the same time become frustrated with owning one because of all of the un-needed attention one gets. It will reflect what he likes to do but not be so ragged out that he can take it anywhere. Best guess would be something from the 80 or early 90's since they're new enough to perform well but old enough to be relatively forgotten amongst the public, without garnering the unwanted attention of the 60's and 70's era vehicles. If he's anything like me, his love of cars sprang from his father, even though he wants to distance himself from him, he'll end up with a semi-similar taste in cars.
Though i could see him in an old shoe-box chevy. I cant explain that one yet.