The big cost deterrent with a 5.4 is the intake manifold: you have to get one that'll fit under the hood, and they are pricey. Hence why a 4.6 is a more economical swap-in; you can get all you need (engine, trans, etc) for as little as $2000, if you find the right deal. Most are probably spending around $3k for everything (parts-only, no labor).

(Thanks for the PM, Stang 007!)

 

3" Cowl hood !

 

..just put one of those big blower intakes on and stick it through the hood...my next project

Seriously though, if the car will be used for offroad/racing, you have a lot more options, IMO, in what you do to it. Takeout ALL the electronic controls, etc., put a big-block motor in it, run it n/a or spray, or turbocharge it...you've got a real beast!

If you have to maintain some sense of streetability and/or need to get it inspected to be street legal (....not as bad here as CA but almost...still have to pass OBDII emission inspections), then you need to take those kinds of things into account as well. They'll see it's a 2005+ car, plug in their OBDII too into it, and run the tests....if there's no PCM or stuff is massively-missing, it wont pass. If everything is "Unavailable", then it will pass. Engine choice, and whether it's electronically controlled or not, will have a bearing on this. Now if you move like 30 miles east of where you're talking about, it's a different story.