All but one of those came in 1986, when he drove the #90 Cox Buick in ten races. His debut went solidly, as he qualified for the race at Daytona. He finished that race in 20th. Three races later, at Road Atlanta, Willingham began a hot streak. He got his first ever top-ten qualifying effort with a ninth place finish and then roared to his first career top-5 with a fourth place showing. After a 25th place finish at Langley, Willingham finished 9th (Rougemont), 10th, (Darlington) and 11th (Richmond) in a row. Willingham's good finishes earned him 31st in points.
Willingham's only made one start in 1987, coming again for the Cox team. He qualified 25th at Daytona and came home with another top-20: 13th. Oddly, Willingham's team released him weeks later in favor of Ed Berrier, despite Willingham's promise. Willingham hasn't raced in NASCAR since.