Pay N Spray is also a mod shop: "your cars can be given paint jobs, new wheels, window tints, grilles, spoilers, plus you can upgrade suspensions, engine and brakes".
I hope the engine part means you can add Blowers and such on the old muscle cars, kind of like the dukes from IV. On that note, I hope if the dukes makes a comeback, it will actually be a little faster. I know the blower version of the dukes was rated at 750BHP, which should mean its ridiculously fast, once it grabs traction.
I hope with the upgrade-able suspension, cars won't feel like you're driving boats around, how they swayed back n forth on IV.