Stock factory TR tires are right at 26" tall. If you're looking for correct mph, you have to stay close to that. On my 255-50s, they advertised them at 27", but measuring them, I found them to be 26.5". I also measued my my fronts, 255-45s, and they were 25.5. If that's the case, I'd think that 245-45s would be more like 25".
Don't forget, it's whatever you prefer. My preference is a taller tire. Just wanted to put out more choices for you. My 17" rims are only 8" wide. I couldn't even consider 35 or 40 series for my application.