My lab often rides in my cars. Always on the passenger side floor. Never allowed my dogs in the seat.

 

I've taken our 85lbs Boxer, ZERO, in the RS a couple of times to Car Shows. I put a sheet over the front seat. He's obviously too big to be in the rear w/ the roll bar.

Unless you have a little dog, I would not put them in the rear.

 

Zero has his eyes locked on the upcoming apex...

 

Put a seat cover on the front seat. I use that and a towel for my German Shepherd Dog.

Granted, you can only carry one dog at a time, but you will double your mileage that way and have twice the fun driving.