The 21x24 flaps are what you need. Just pair them with these brackets for the rear wheels, https://www.sharptruck.com/truck-hardware-custom-fit-mounting-brackets-gb759895
If you would like the full truck set you can find it here, https://www.sharptruck.com/ford-f450-f550-blue-oval-gatorback-dually-mud-flap-set-gcr41f-4-gb2124f-c-gb759895
No, the rear flaps will not fit the 2023. Gatorback has them designed and in production. They are just waiting for Ford Accessories to give the go ahead to start selling them. As soon as we can they will be published on the site.