Originally Posted by AStrong1

thanks for the information. What about the guys that do AIR/smog deletes? Do they have to buy new cats or can they just run stock?

Originally Posted by Conanski

GT40 heads and an intake based around the 5.0 truck intake design are what all of these 5.8 motors should have come with IMO, there wasn't enough of a difference between these two engines from the factory and all the "289 parts" they used really hold it back.
If you want a set of these heads you have to find a '96-97.5 Explorer, a Gen1 Lightning, or one of the super rare 5.0 Cobra Mustangs. Later Explorers used the GT40p head which actually performs slightly better but requires special headers or the stock manifolds but those limit their potential. If you find a lightning the intake(both upper and lower) would be worth grabbing too but none of 5.0 versions will fit a 5.8.

If you just put GT40 heads on your truck motor that will add some power but not as much as it should, the exhaust and intake need upgrades to get the most from them. The exhaust is easy just take it all off and replace it with just about anything aftermarket and include at least shorty headers. The 5.8 truck intake isn't the best or worst thing in the world but the lower portion is definitely the bottleneck, if you have it off to do the heads port the blazes out of it and open up the exits to match the heads as much as possible.

The last piece that will really wake it up is a cam change, something like the Comp 35-349-8 would complete the package and make it a solid 300+ hp motor, this last part gets complicated and expensive though as it will exceed the limits of the factory fuel supply components requiring upgrades to those parts and the EFI computer at the same time.