I've seen a couple different television shows building headers using a kit with plastic pieces with various bends and lengths that are assembled to mock up the headers then metal pieces can be cut or formed to match that pattern. They could also be used to mock up roll cages and even railings. They appear to work really well so I looked them up. I was thinking probably a couple of hundred dollars but I was way off. There are different size kits as far as tubing diameter and 4 or 8 cylinder but the kits with the large number of pieces are $1,500. Not likely something anything other than a very large shop would buy. It would probably be cheaper to have a shop build the headers than to buy the kit. A large shop that makes a lot of headers and roll cages could probably justify them at that price but the average guy that watches these shows isn't likely to buy them. I assume the shops in the shows these were on got them free or just to use for the episode.