To answer your question correctly without getting all G5 classified and Area 51 conspiracy on you.
SATB - 1977 Special edition T-top auto 400 (6.6 litre)
SATB II - 1980 Special Edition T-top auto 301 turbo
At least that was what they wanted you to believe the car was in both movies, regardless of what parts, motors, NOS, year, etc people have been told throughout the years.