The base 1970 Coronet is the car under the trim badges. Same 117-inch wheelbase as the Super Bee and R/T, same B-body unibody, same suspension geometry — but with steel wheels, vinyl bench seat, manual everything, and the 225 Slant Six as standard. Volume sales went here; collectors went elsewhere.
Engine options on the base car ran from the Slant Six (B code) and the 318 2-bbl V8 (G code) up through the 383 4-bbl Magnum (N code). The 440 and Hemi were not available on the base trim — those engines required the R/T or Super Bee. Plant: Lynch Road and Hamtramck built the volume; St. Louis ran lower numbers.
Plenum decodes base Coronets through the same 1970 B-body broadcast schema as the performance trims — the body code in VIN positions 1–4 tells you which trim level (Super Bee WM, R/T WS, etc.) you have. Wagon and 4-door body codes are out of Plenum's wheelhouse for now; the 2-door coupe and hardtop are the focus.