I haven't had a plug ejection problem yet, but will 3 or 4 valve heads fit (bolt up) on a '99 5.4? What other stuff do I have to change to make this work? i.e. intake manifold, exhaust manifold, computer, etc.
If I have to change the heads I might as well go for the best available.

 

If you are concerned about spitting plugs, I think you would be better off buying new 8-9 thread heads and having them ported.

Way too many things to change to make the other heads work.

 

The 3V blocks are also revised. You would have to change all of the electronics, wiring, intake, exhaust, etc to change to a head other than the 2V PI heads.

 

If you wanna go 4V might as well find a totalled Navigator or Blackwood and get the engine, pcm and harness from that. Might also need parts of the key ignition system and the oem key too.