Easy on the throttle and long, steady road speeds would likely give you 40-42 mpUSg. Start rowing the box, and having your way with her and 34-37 is more likely. Colder temps could drop it 2-3.
As mentioned, this is a more aggressive combination of cam, valves, flow characteristics, and riding style.
Probably not worth an extensive refit to get a few more mpg. Crank it, rip it, and enjoy it! (She'll love you for it!)
That said, a meticulous tune-up performed every 4000 to 6000 miles will optimize the factory settings and likely give you around +3 mpg.
"Ain't she sweet?" (Walt Kowalski [Clint Eastwood], Gran Torino)