Ben, nice guess, but not the one I'm thinking of. Keep try-en.

Are you asking for the last team to win the Cup title and not return to compete the following season)? My research indicates that Carl Kiekhaefer's 1956 championship season was his last cup season with Buck Baker earning the title. The team was sponsored by Mercury Outboards. Baker would win another championship in '57 driving for himself.

"FINAL RACE: Wilson, NC - Buck Baker's championship season was not without controversy, and the season finale at Wilson Speedway was no different. Joe Weatherly was leading the final lap when he ran out of fuel on the backstretch. He came off Turn 4 without power and beat a surging Baker to the finish line by two car lengths. However, Carl Kiekhaefer protested on the grounds that Baker had reached the scoring stand before Weatherly and the scoring stand marked the official finishing point instead of the start-finish line. NASCAR concurred and Baker was awarded with his 14th victory of the season and a 586-point victory over the inactive Herb Thomas. Speedy Thompson's third place finish, compared with Lee Petty's ninth place finish, allowed Thompson to overtake Petty by a mere four points for third place in the final standings." NASCAR.com.

Other understandable misnomers -

1992 - Alan Kulwicki - His AKI team was ultimately purchased by Geoff Bodine following his death in April 1993; The independent Wisconsin native drove for his own team through the spring of 1993.

1989 Rusty Wallace's Kodiak Pontiac and Ray Beadle; Beadle owned the #27 team through the 1990 season; Wallace didnt drive for Penske until 1991.

1980 Dale Earnhardt's Mike Curb Records Chev./Olds and Ron Osterlund. Osterlund had other business interests to attend to so he sold the team to the controversial J.D. Stacy during the 1981 season. Earnhardt would ultimately leave the now-Stacy owned operation for his future owner that he became synonymous with - Richard Childress;