The stock K-member does not wear out, but it can rust out. The factory K-member is generally stronger than all but a few of the aftermarket tubular K-members. In fact, putting a tubular on a street car can be a bit of a hazard, since most of them are designed for drag racing, and aren't really up to the daily challenges of rough roads, pot holes, curbs, etc, that can cause them to break. There are a couple of possible advantages to a tubular K-member. The primary is weight, and on a drag car, every ounce counts. It's actually not that much lighter than a stock K-member. The second is control arm angle for better handling. The biggest advantage to a tubular is that it doesn't become a collection tray for 8mm sockets, and makes working on things like starters and exhaust easier. Generally a tubular K-member is not a recommended mod for a street car.
Kurt
