Montaz3,
I like your idea for deleting the seat and bolting in a car seat! Isn't if funny how women usually don't like our creative solutions!
But I think you will have plenty of room in the back of your mustang for the car seat. I would suggest mounting the seat in the middle so that he/she has plenty of leg room, and it makes it easier for you to watch the him/her from your rear view mirror.
As for her having a supercab F-150, I do too. And I have THREE car seats in the back of my truck!!