The parts book lists replacement parts, not necessarily what came
on the car from the factory. For instance, all, over the counter
lower control arms came with sway bar brackets, no matter if the
car they were going on had a sway bar or not. The dealer data book calls out .88 sway bars for small block cars and .94 for the 383s.I'm guessing, because of the low volume of big block cars built, and the small number of bars they sold, they just sold the smaller bars for everything.