The Ford Mustang Maxum GTP was an IMSA GTP sports racing car built by Roush Performance in 1987. Based very loosely on a production Ford Mustang, the car featured completely new bodywork, and used a mid-mounted Ford V8 engine; initially a 6.5-litre unit, it was soon upgraded to a full 7-litres. The car bore little relation to the earlier Ford Mustang GTP, which was developed by Roush and Zakspeed in 1983, and featured a 2.1-litre turbocharged Cosworth BDA straight-four. Although the Mustang Maxum GTP was capable of matching the dominant Porsche 962s for pace, reliability gremlins restricted it to two podium places.
After the spectacular failure of the Ford Mustang GTP in 1983 and 1984, Ford had withdrawn support for the car, and Roush Performance withdrew from the project as well, to focus on V8 engined cars. Three years later, they came up with their own GTP Mustang, which was named the Ford Mustang Maxum GTP. Unlike the 2.1-litre turbocharged Cosworth BDA straight-four that the Zakspeed/Roush Mustang GTP had used, the Maxum GTP used a Ford-based V8, initially of 6.5-litres. Also unlike its predecessor, which was front-engined, the engine was fitted in the middle of the car. Roush Performance ran the car themselves under the "Roush Racing" banner, and debuted it at the 1987 24 Hours of Daytona, selecting Scott Pruett, Pete Halsmer and Tom Gloy to drive it; however, suspension failure after 120 laps consigned them to 58th place overall, and 14th in the IMSA GTP category. The next round of the IMSA series, which was the Grand Prix of Miami, proved rather more successful; Pruett and Halsmer brought the car home in third, beating seven of the eight Porsche 962s that finished the race, as well as the works-entered Jaguar XJR-7.
The Grand Prix of Atlanta, however, saw them retire after 45 laps, restricting them to 22nd overall, and ninth in the GTP category. Although the team finished the next race, which was the Los Angeles Times Grand Prix, they could do no better than 15th overall, and seventh in class; last of all those still running at the end of the race. Things didn't improve at the Monterey Triple Crown either; a blown engine after 25 laps saw Pruett finish 22nd overall, and 12th in class. The Lime Rock Grand Prix saw a strong return to form, as Pruett and Halmser took second overall, finishing 37 seconds behind Al Holbert's Porsche 962; Holbert's 962 and the Mustang Maxum GTP were the only two cars on the lead lap. Davy Jones was selected to drive the car at Grand Prix of Mid-Ohio; he retired after 23 laps, being classified in 23rd overall, and ninth in class. By now, the car had been fitted with a 7-litre version of its Ford-based V8 engine, and the 3 Hour Grand Prix of Palm Beach, where Pruett was partnered by Whitney Ganz, saw the team finish in tenth overall, and fifth in class. Halsmer returned to partner Pruett at the Camel Continental; the team, who were now running under the Applicon/Roush banner, retired after 98 laps and were classified in 15th overall, and fourth in the GTP category. Two further entries, at the California Grand Prix and the Grand Prix of Southern California, were lodged; but the Mustang Maxum GTP did not run in either of these, and never ran again. Pruett, who had driven the most races with the car, was classified 16th in the Driver's Championship, with 47 points, whilst Halsmer was 19th, with 41 points.