My various Ford picks:
Escort RS Cosworth
Mustang (3rd-gen) SVO
Mustang (4th-gen) SVT Cobra R
Mustang (5th-gen) Boss 302
Mustang (7th-gen) Dark Horse
Mustang (7th-gen) GTD
Mustang (7th-gen) GT4
Mustang (7th-gen) GT3
Thunderbird (1st-gen)
Plus I'd add a couple models originally made for the Australian market, like the classic Falcon that was the basis for the car used in Mad Max, plus a couple relatively newer models, like the FPV Typhoon.
I'm also unsure if we'll get an actual GT4-spec Mustang, but if not, I'd be down for a made-for-game "Gr.4" version like we see for the majority of brands.
Speaking of which, I think more Gr.4/Gr.3 cars should be the focus over other race car categories, since those two seem to be the focus of the Manufacturers Cup. Don't get me wrong, I totally want to see the 2024 GT500 trio, the DTM cars from Aston Martin/BMW/Mercedes-AMG, plus various LMDh/LMH cars to come to GT, as well as maybe a few classic LMP900/LMP1 cars like the Audi R8 that gave the road car its name, or the BMW V12 LMR. But I think there needs to be a way for Gr.2, Gr.1, and maybe even Gr.B to be integrated into the Manufacturers Cup, or at least something like it, as you'll notice that every time there's a Gr.1 race at Le Mans, everyone just opts for the classic Group C racers. Although I still think those cars belong in Gr.1, I think this over-centralization - similar to a race when everyone picked the TS020 for Le Mans, despite it being open to all Gr.2 machines - could definitely be addressed if it were part of the Manufacturers Cup, where I feel like there's a notably wider variety in the field. I also wonder if adding multi-class racing would help, too, but I don't think that'll be integrated until the next installment, where we are likelier to also have larger fields overall. Of course, you could still feature them in Online Time Trials, or in new rounds of World Circuits events, but otherwise, I'd like to see much more field diversity in various Sport Mode Daily Races and championship rounds.
Personally, for the time being, I'd prioritize updating the Gr.3/Gr.4 entries for the brands that have the oldest entries, or at least those that can be updated. (Sorry Mitsubishi/Citroen/Dodge!) Ferrari and Hyundai especially come to mind, with the 296 GT3 being perfect for the former at least. I'd also be absolutely down for even more brands to join the Manufacturers Cup, just we've most recently seen with Genesis and Suzuki. Maserati honestly seems like one of the most obvious picks, since it has a very rich motorsport history that continues even to this day. I could see the MC20 GT2 being put into Gr.3, and then for a Gr.4 car, they could add a made-for-game GranTurismo Gr.4 based on the newer model.
I also would not discount older race cars, especially for brands like the aforementioned Mitsubishi and Dodge. The GT300-spec FTO from the turn of the millennium could become another Gr.4 entry for the former, while the latter could get an additional Gr.3 car in the form of the iconic Viper GTS-R Team Oreca. (I also don't know if I mentioned this already, but I think the GT300-spec Lexus LC500h from the 2021 Super GT season would be a wonderful way to update its Gr.3 offering.)
