Well apparently 5.4's are hard to come by where i live however there is a large amount of 4.6s at the junkyard. Is this theme because they are notoriously junk? Because if not right now im seriously thinking about swapping out the 4.2 to a 4.6, but idk is it really worth that 28 extra horsepower or whatever it is ???

 

I looked into it one time for curiosity's sake and found it to be way more work than it's worth. It's not like going from a 4.6 to a 5.4, they're practically the same motor right down to the engine mounts and fuel rail and harnesses and stuff. A 4.2l is from a different family of engines and has pretty much nothing in common with the 4.6 and 5.4. I'm sure it can be done but I couldn't find any good write ups or anything on it online. Hopefully someone can give you better news, but I pretty much came up with it being too hard.