There wasn't one in US delivery models. You chose your radio from the accessory catalog and it was installed by the dealer, Most customers in New England chose the Blaupunkt.AM/FM cassette.
Edit: In '83-'84, Turbos had Sony systems with the amplifier under the back seat. They had constant buzzing noises from running signal wires all over the place. Then, in '85, they partnered with Clarion for a whole new can of worms.
My dad's '83 had that buzzing noise, and after many years, in '85, they replaced it with a Clarion that worked very, well. My '84 never had a problem with the Sony though. It wasn't pretty but it worked well.