It looks like the RTS Suspension on an Astre consisted of BR70X13WL (white Letter) Tires on the Rally II wheels, 1" front sway bar, and a undetermined width rear sway bar. So on a Sunbird, probebly nothing more than the upgraded handling package on a Monza Spider, 1 1/8" front bar, and 3/4" rear bar correct?
The only differences would be Weight (how much less does a Coupe weigh?), Gearing differences, and individual car prep, ( Tuning) And some identical cars are just faster then others due to build variences, and driver.
And as for the Girl I dated with the 79 Sunbird, all I can say is that SHE finished Collage & traded up!!!!! And the last time I met her she was Married with 2 kids and was driving a Mazda MPV!!!! but that was 15 or so years ago,
And her Sunbird was only Fast compared to my 18.8 second Firebird. She was a Cutie Back in the Day.
78 Sunbird Safari Wagon, 3.8 N/A, 1971 Catalina Freeway Enforcer
77 Astre Formula, some day soon powered by a 215 Buick V-8
1973 4-speed Lemans Safari STOCK!!!!! 1978 Catalina Safari
1971 Lemans Safari/GTO Clone, 1969 Firebird Sprint 301 ci OHC6, T-5, 4.10 12 bolt posi