the regals did not have the chevy 305, its either a 3.8 buick v6 or a 5.0 olds 307 or a rare diesel in all regals at least 81 if not 78 though 87. there are some years, 84 for sure, that the 3.8 was the only option. i think there may have been a 4.1 in rare cases but i dont recall reading or seeing that for sure.