Rossi 1971 Challenger was built by a chassis builder that had built a bunch of Mopar cars fro drag racing, I can't remember his name right now but he was from Austalia is what I remeber. I think his shop was in or near Santa was his shop was in or near Santa Monica,. CA Ron Butler was his name; He was the drag racing chassis guru at that time, especially for all out sportsman cars up: I don't remember hearing anything about Paul being told to quit racing that car by NHRA but I wasn't in his crew or real close to him either He got into road racing Mopar stock type road racing spec. cars, not all out NASCAR or SCTA all out road racing cars, is what I'm remembering now CRS on the proper series name now
Yep, Ron Butler was his name. He built the Mopar Missile Duster, Butch Leal's Pro Stocker and SS/B 1965 A-990 car and others. Ron was a top notch chassis guy. I forget what the exact technical infraction was with Paul's car. It may have had something to do with weight distribution (too much over the back wheels).
He was the drag racing chassis guru at that time, especially for all out sportsman cars up: 
