The idea was that the gassers, to be legal, had to have all the operational systems that a street car would have, like full floor, interior, fenders, hood, etc. Some people stretched that ruling to take as much advantage as possible.
There was a car, in a 3 part series in Hot Rod Magazine, and built by Don Long that they called the Ultimate Gasser. They took each rule and bent it just enough to be legal, but to make the car as light as possible. For example:
Rules said you had to have two working headlights. But the rule didn't say how bright or big they had to be, so they installed two penlights behind the lenses, and called that legal.
Rule said you had to have working shocks. So they built two shocks that had no guts in them and weighed only like a pound each.
Rule said you had to have a full interior. They upholstered the car with aircraft upholstery that was super light.
Rule said you had to have operational windows, so they used seat belts to raise and lower the plexiglass side windows.
They stretched the rules in every area just to see if they could get away with it, and at the first strip they took it to they were turned away as the car was just too radical. I forget if they ever got it approved to run, but it was a fun exercise in cheating the system.
Don