This is great advice from Ken - I won't do ANY welding on a car unless I've got a person standing by with water and a fire extinguisher. It's just way too easy to lose track of whats happening when you are wearing a welding mask. Your welder is capable of creating enough heat that almost anything in the car can quickley catch on fire. You should also have the car set up so that you can IMMEDIATELY roll it out of the garage if things go really bad - Don't have it up on jack stands with all the wheels removed and three cars blocking the garage exit!!