MoparPartsGiant.com offers the wholesale prices for genuine 1984 Jeep J20 parts. Parts like Booster & Master Cylinder are shipped directly from authorized Mopar dealers and backed by the manufacturer's warranty. Parts fit for the following vehicle options. Engine: 6 Cyl 4.2L, 8 Cyl 5.9L. Transmission: 4-Speed Manual Transmission, Automatic Transmission.