Hi, I drive a 1991 Chevrolet S10 Blazer, 2WD, 2Dr, 4.3 Liter Engine. My question is what is the firewall made of? Steel or aluminum? The truck suffers a classic Chevy condition; rust. I need to know what the firewall is made of because the rust has eaten all the way through in several spots on the floorboard (to the engine compartment). To repair this, I first need to know what the firewall is made of. I believe back then it was steel. Then, I need to figure out what tools I need, what materials I need, and what the steps are to sealing and repairing these holes. This will probably involve some welding. Please, give me your input. I need professional advice on this, as well as advice from anyone who has done body work on cars and trucks.