I'll go against the grain here. I thought I only needed to replace the passenger side front floor due to a leaky heater core at some time. I put the car up on the Roto and took the undercoating off and I was I surprised. Three frame rails will need to be replaced. One rear rail was completely coated and completely toast. The only thing holding it in shape was the undercoating. It is up to each individual but I would go the whole mile on this car if you plan on keeping it. Sometimes you can be pleasantly surprised and sometimes the surprises are just plain scary.