An unnamed muscle car is due to appear in Grand Theft Auto VI, parked at an apartment complex behind a hammer-wielding woman in Hamlet in the first trailer and shown again in a bonus Ultimate Edition screenshot where a visible logo suggests the name Sirius. It appears to be based on the 1969-1970 Mercury Cougar, with the screenshot version evoking the Eliminator package rather than the base car.
Vehicle data via GTA Wiki (Fandom), CC BY-SA 3.0.