Will you have a passenger in the front seat? If not, something like an E36/46 would work. Just put the car seat on the passenger side and slide the front seat up a bit. The coupe did seem easier to put a single child into, which is counter-intuitive.
The snap-in infant carriers aren't much of an issue. It's the rear-facing convertible car seats that take up the most room. I've found that once they flip to forward facing (now recommended only after they turn 2), things get much easier.
All mine are in boosters or forward-facing right now. I've had no issues with either in my New Edge '01 Ford Mustang GT. Haven't tried rear-facing, but if you're interested, I could see if it could work.
The answer is Fiesta ST. My 2-year old (front-facing) fits in the back seat in his car seat just fine, and I can still fit 2 more adults plus me with some room in the hatch for our stuff.
If you like the feel of a boosted Civic, you will die for this thing!
T.J.
PowerDork
8/20/14 9:24 a.m.
I seriously doubt that any kid that still needs to sit in a car seat should be autocrossing. How could they even reach the pedals? 
protégé 5, bonus on being able to fit a stroller in the back as well.
I got the Focus ST for the kid and autocrossing. Fits the kid seat just fine in the back forward facing and should be fine rear facing in the center or behind the passenger. I think the Fiesta is too small for a rear facing seat, but would probably okay with a forward facing one. As it stands though I'm 6'1" with long legs and when I'm in a comfortable spot there isn't a huge amount of room in the Focus for her seat behind me when forward facing.
That said, if you have a rear center mounted seat in either car you likely will not fit an adult next to it. Ideally that is what you do, but obviously I'm doing the front facing mounted on the driver side now that she is 3 years old. The seat is a Britax with side protection.
These are some pics of me in the back of the Focus. I have long legs.
The Focus ST is very fun at autocross. Rotates very easily and has tons of power, probably too much since it has no limited slip out front.
