The mechanism mounts fairly high up on the firewall...not the floorpan. That's not to say your car didn't need metal work where the mechanism bolts on though. The mechanism uses studs where it goes through the firewall. There should be two holes for the studs...then the nuts are installed from the wheelwell. If you can't find measurements for the holes, you could remove the studs, attach the mechanism to the kick panel and mark the hole locations.