Complex sentence: A four-door hardtop body style joined the sedan in 1967 fitted with a 383 cubic inch V8 engine whilst the sedan continued with the smaller 318 cubic inch V8.
Split into simpler sentences: A four-door hardtop body style joined the sedan in 1967. The new model was fitted with a 383 cubic inch V8 engine whilst the sedan continued with the smaller 318 cubic inch V8.