The decade saw the concept of "customer chassis" take over the series, as well as exclusive engine leases creep into the competition. Nearly all engine and chassis manufacturers were foreign-based, to a point where by 1987, not a single chassis entered was built in the United States. Manufacturers such as March, Lola, and Reynard were the chassis of choice on the open market, with other more exclusive chassis (Penske and Galmer) also experiencing success.