Guys, that's a little different situation, where the welding machine sits on the back of the truck and the truck's bed is part of the welding circuit along with the vise. You even have 120v outlets on some of those beds as well, and all are grounded through the bed back to the welding machine/generator.
I just like to take certain precautions when welding on somebody else's vehicle. I can't afford to buy computers for cars that I might weld a hanger clamp or muffler on for them. $20 welding job that ends up costing me a couple hundred does not seem like a good business practice.
I was just giving a word of caution that was worthy of noting,
Have a good day,
John Wright