Complex sentence: As the 289 had served many years as the staple v8 engine for the early and mid 60's, the time had come for more power, increased longevity, and easy emission regulation that would be needed to enter the 1970s.
Split into simpler sentences: As the 289 had served many years as the staple v8 engine for the early and mid 60's. The time had come for more power, increased longevity, and easy emission regulation that would be needed to enter the 1970s.