If you are going to mount a fire extinguisher inside your car, make sure it can't come loose in an accident an injure someone. I would suggest along the passenger floor. Be certain to use a metal mounting bracket. Your best bet would be to buy the whole set up from a place like Racers Wholesale. The SCCA requires in car extinguishers for Showroom Stock, Touring and Improved Touring classes. Their only stipulations are type, size, and metal mounting brackets. There was a fella from up here in Mass who crashed a T1 Corvette at Pocono a few years back. The extinguisher came loose in a side impact and hit his head, killing him instantly. I cringe every time I see one of those kids riding around with an extinguisher mounted to the plastic A pillar trim in a ricer car.