yes they are the same as 4.6L DOHC heads, except for slight port and chamber differences. the 4.6/5.4 is called modular because A) ford can use the same tooling for all the motors, and B) you can swap components onto all the motors in the family, pistons, heads(except for the 6.8) and other things.
all depends. power results have ranged from 30-70rwhp. also there are supporting mods that should be done as well. like i was planning on doing the headswap, but then i realised my motor has 103xxx miles on it and why am i putting on heads that will increase the compression and make more power especially with unknown previous owners who i dont think took very good care of it. now im just gonna buy a new bare block, build it with forged crank/conrods/pistons, and finish it off right with all ARP hardware.
yes they are the same as 4.6L DOHC heads, except for slight port and chamber differences. the 4.6/5.4 is called modular because A) ford can use the same tooling for all the motors, and B) you can swap components onto all the motors in the family, pistons, heads(except for the 6.8) and other things.
the lightning is SOHC. there are DOHC heads that come off of a 5.4 but they are either from a 00R(unobtainable), a navigator, a GT(fairly unobtainable) or a BOSS 260/290 from australia.
they will physically bolt up to a 2v block, but you will need a different front cover as well as various other sensors. you would also need an inlet manifold for DOHC heads. you will experience a loss in compression due to the larger combustion chambers on the 4v heads.
generally with 4.6 motors, its easier to do headswaps with the motor out of hte car. i know people will do them in the car, but then you have a rather small work area. i guess im spoiled because i have access to an engine lab and pretty much every tool snap-on has to offer.