GMPartsGiant.com offers the wholesale prices for genuine 1989 Buick Regal parts. Parts like Automatic Transmission Case & Related Parts are shipped directly from authorized GM dealers and backed by the manufacturer's warranty. Parts fit for the following vehicle options. Engine: 6 Cyl 2.8L, 6 Cyl 3.1L. Model Code: CUSTOM 2 DOOR, LIMITED, REGAL.