Junkyard speed parts:
The '96-'97 5.0 Exploder (Mountaineer) had GT40 heads with 3 small vertical bars cast into the front. Approximately 62cc combustion chamber, 1.84" intake valves, 1.54" exhaust valves. Any header that fits an E7 head will fit these.
The '97.5-'01 5.0 Exploder (Mountaineer) had GT40P heads with 4 small vertical bars cast into the front. Approximately 58cc combustion chamber, 1.84" intake valves, 1.48" exhaust valves. Your O.E. shorty headers will fit these but, very few aftermarket headers will fit due to the angle of the spark plugs.
5.0 Explorer Intake manifolds(internally identical to the Cobra):
The Fox Mustang uses and internal EGR just like the '96-'97 Exploder. You'll also have to drill and tap the lower intake for your ACT sensor.
The Explorer has a better injector than the Mustang and Mark VII that provides better atomization.
If you want to get really wild the 300 six and '87-'88 T-Bird and Cougar 5.0 have 15 lb/hr injectors as opposed to our 19 lb/hr. I've always wanted to mix and match O.E. parts to create a lean burn Fox.
Our cam has slightly more lift on the intake lobe and more duration on both sets than the Explorer. On top of that the GT40P heads would bump your compression up slightly.
With the Explorer intake(s), GT40P heads and your short block I would expect about 275 hp at the crank with better than stock f.e.
Then add a 2.5" H or X pipe and a free-flowing cat back with some under drive pulleys and 1.7:1 rockers and you'd have one angry Fox!