Legally there is no possible way.
Engine has to be at least as new/clean emissionwise as the body or newer/cleaner = FAIL
5.0 is a dead horse in that regard even before you slap on a EFI system intended for older things and really has no consideration given for emissions. If you have any kind of emissions check and your model year is 1973 or newer I think the Sniper could be hard if not impossible to pass with especially if they want to get nit picky.
That is a federal thing, whether or not the yokels will enforce it is another thing, you might ask them for sure.
Newer trucks are more electro-digical in the dash and are harder to swap than the older ones too, I think your 04 is on the wrong side of the cutoff (if it isn't it is close)
State laws vary wildy. Im sure someone from your state will chime in but if they do strictly obd2 emissions scans like they do here in NJ you may be out of luck and need to use a factory EFI system from an explorer. The Holley system is made for performance and not to meet OBD2 emissions standards. I have the Holley system on my 65 mustang and it's awesome but I don't get my mustang inspected anymore (old enough to be exempt).
Emissions check for a '65 is "well, it doesn't seem to smoke too bad..."