The best hp numbers I've seen:

Gains of up to 25 HP and 40 ft/lbs (4.6L & 5.4L 2-Valve engine) with a Gryphon.

You might be able to eek another 5-10 out with the Gotts mod and a custom tune.

Power Hungry Performance - Gryphon Dash Mount Programmer for F-Series Gas Vehicles