[mpanten]

I have had both motors and both are good. You need a blower to make good power but there is plenty of aftermarket support for mod motors, especially the 4.6. You can run up to 9psi on pump gas with the standard 2valve 4.6 and not need to upgrade. If you go higher you will need forged internals.

The 4.6 4 valve is already forged and will naturally put out a lot more power. Not sure about the internals of the 5.0 and 5.4
Anything over 6psi you will need the intercooler. If I had to worry about emmissions I would be looking at the mod motor kenne bell supercharger system for sure. I worked great in my mustang.