Engineering? Probably not. More like a marketing decision when you wouldn't dare sell a top of the line Chrysler with the same engine as a lowly Plymouth.
Even GM and Ford had totally different engines for their various makes. Keeping up with the joneses I suspect.
GM started going wobbly in 1975 when they put Chevy engines in some Oldsmobiles without informing buyers. Ford started putting Lincoln 430's in T-birds (optionally) in 1959. They're all about as pure as New York snow.
July 19th should be "Drive Like Rockford Day". R.I.P. Jimmie.
