To start with, this is Cody; I figure we should make a new account for the shop itself, but since this one has some post history I'll use it for now ;-).
I might be a bit biased, but I've got to throw the Garage Karthaüser / Black Forest Racing green and orange 914-6 in the mix. It's probably the most successful yet unheard of 914 race car in history. The car was originally built into a race car by none other than Kremer Racing... you know, the multiple-LeMans-Winning-Team that built most of the 935's, the 1981 917, and many of the 962's among a series of thier own branded cars. The car was sold to Michael and Reinhold Karthaüser in early 1971 and began it's racing career doing a handful of GT races at Spa-Francorchamps and Nurburgring, but mostly ran hill climbs in Belgium and western Germany. In it's original career under Karthaüser it won at least 25 races (we have the results sheets), but we know there were more that we don't have hard record of. My father bought the car in 1988 and began racing it two weeks later. With my father driving the car it continued winning races. I'm still looking for better records, but it looks like the number will be well over 100 race wins. It even went pro-racing again in the early 2000's with a startup series called ARL where the car won a few races overall and took the inaugural championship with my father and Joe Cogbill driving and beating Randy Pobst, Michael Galotti, and other future World Challenge drivers and teams. In 2003 the car was crashed badly by a co-driver at The Walter Mitty Challenge (while leading for the record) and the wreck was put in storage for a decade. Two years ago my father decided he had been out of racing long enough and re-tubbed the car to bring it back to life. Since September of last year I have shared the car with him at a few events and won 9 out of 10 races entered (finished 3rd at Indianapolis this summer).
The Sonauto car only did well in one race, while a great achievement to finish where it did at Le Mans it did nothing else ever. The Brumos / Peter Gregg car had a way better original pro career, but was also then subjected to a mostly dormant life until it started vintage racing in the late 80's... where it was regularly beaten by our car ;-). The Automotion / Garettson car (which we maintained for 15 years) is another with one or two great years, but then it's been collecting dust since we stopped racing it in about 1992 (and before about 1987).
1971 @ Tros Marets (1st place finish securing the 1971 Hillclimb Championship)
1975 Publicity Photoshoot for Coca-Cola whom sponsored the car for a few years:
1976 when it was put in it's current color scheme:
1988 St. Petersburg Grand Prix:
About 1998 at Daytona pulling away from Hurley Haywood in Brumos' other 914-6:
2000-ish @ Moroso (now Palm Beach International Raceway):
2015 with me driving at Indy: