I checked with Bob Archer from Archer Brothers Racing and he said to Mig or Tig for better penetration .. he said there are no stead fast rules on which to use but they do check out the welds and the better they look the better your chances are of passing the inspection

excuse my spelling...i meant to say if the cage is being bolted to the car.....not car to the car lol.

Thanks for the info, really helped me out.