The things will be accessible in the store between Rocket League Items December 9, 2021 and December 22, 2021, so assuming you're keen on them you'll need to get them before Christmas time. Assuming you need the vehicles and their related things, you can buy them independently for 1100 Credits each or all together for 2000 Credits
What's going on in the Rocket League and Ford Mustang collab?The Rocket League Items Shop Ford Mustang Shelby GT350R RLE Car has the Dominus Hitbox. You'll likewise get these customization things alongside it: