Complex sentence: There were two engines offered initially including a high-revving 4.7-liter V-8 and a higher torque but lower horsepower 4.9-liter V-8; only the smog restricted 4.9 was available in the United States.
Split into simpler sentences: There were two engines offered initially including a high-revving 4.7-liter V-8 and a higher torque but lower horsepower 4.9-liter V-8. Of the two, only the smog restricted 4.9 was available in the United States.