Los Angeles built primarily for the SouthWest U.S.
As far as the same line of car ('A' , 'B' or 'E' bodies) being built in more than one plant ; I can only imagine that the L.A. facility took the slack for popular models that were not Special Orders (e.g. , certain "999" paint colours , special order trim / options , and-or 'B' Body police / fleet orders).
What didn't L.A. build ?
- Convertibles
- 426 Hemi (excepting , supposedly , 1967 GTX / Coronet RT )
- 1970 Dart ( all of those were built in the Windsor , Ontario plant for some reason ... maybe because the Duster and the 'E' bodies were incorporated in Hamtramck and St. Louis ?)
- Exports ( "Y09" / "I")
L.A. ostensibly built "49 State" vehicles (read: non-N95 cars) , in a similar vain to Van Nuys G.M. Plant building Pontiac 400 and 4-speed-with-V8 Camaro & Firebirds ; combos not available in Ca during the "Automotive Dark Ages : Mid-Late 70's"