NASCAR did not allow Petty to bring in a back-up car----although back-ups were permitted earlier in the year at Daytona, and would be permitted at 'Dega later in the year. Veteran independent D.K. Ulrich offered to let Petty drive his US Racing Chevrolet in the 600. Petty started 37th, but went out on lap 123 with a blown engine.
DE won the race. At one point he was about to go a lap down.