I think even better would be to get the car down to 3200-3500 lbs...It's almost like you don't really want more displacement and more power. I do.
This is a good place to tell Ford and their competitors what we want. I think the Dodge competitor to the Mustang is too large and heavy, but I like what Dodge is doing with larger engines. Ford may never get my money again if they don't make small cars and their Mustang is emasculated.
If you like porky cars with small engines or really complex hybrids - definitely speak up.
To me it's important to consider the entire package. I think the 2.3T would be more than impressive in my Fiesta ST, but in the Mustang it's ok, not great.
Yes, around 580 would be a good hp total and I would buy a new regular GT (not a limited production car that dealers mark up to a higher price) if it stayed at a reasonable weight and had that amount of power.