One of the most successful collaborations between a major car company and a small aftermarket outfit was the deal between Hurst and Oldsmobile. Back in the late 1960s, Hurst transformed the Oldsmobile 442 into one of the fastest cars available on the North American market (via Driving Line).
Oldsmobile shipped partially disassembled 442s to Hurst where they installed the biggest engine Oldsmobile had, the mighty 455 V8 with 390 HP. The Hurst Olds package also got numerous other performance upgrades like the ram air induction system. They also added a heavy-duty suspension and brakes.