Here's what you'll be able to drive in the new Forza game.
Forza Horizon is a spinoff based on the original Forza Motorsports series, which replaces real-life race tracks with semi-realistic depictions of country roads. The original Horizon game took place in Colorado, and the last Horizon 3 game was set in Australia. Horizon 4 was just announced, and will be set in England. The trailers showed us some of the cars we'll be able to drive, but some PC gamers were able to download data from an early copy of the game, and have leaked the entire car roster. This list contains spoilers, so be warned.
The leaked list appeared on Reddit, and is simply too long to post here. The massive list boasts 450 cars, including the barn finds that will be found in the game. These include a 1960 Aston Martin DB4 GT, 1983 Audi Sport Quattro, 1930 Bentley Blower, 1986 Ford Escort RS, 1964 Ford GT40, 1993 Jaguar XJ220, 1997 Lotus Elise GT1, 1970 Land Rover Range Rover, 1965 MG MGB, 1965 Mini Cooper S, 1962 Peel P50, 1998 Subaru Impreza 22B, 1962 Triumph Spitfire, 1998 TVR Cerbera, and 1977 Volkswagen GTI. Since the game is set in the UK, it isn't supprising that 10 of the 15 barn finds are from British marques and two of the Fords are UK-designed models.
There may still be more cars added through DLC or expansions, so this list likely isn't 100% comprehensive. Most of the cars on the list have appeared in previous Forza games, but some notable new entries to the franchise include the 2015 Audi S1, 2019 Ford Mustang GT, 2017 McLaren 720S, 2018 McLaren Senna, and 2017 Mercedes Unimog. There are also some returning favorites from past Forza games, so be sure to check out the full list over on Reddit.