I've been pondering the 5.4L 4V swap since we've purchased this car. I think it stands to reason that since the 4.6 2v --> 5.4 2v swap is so direct bolt on, that the 4v --> 4v swap would be equally the same (all 4.6 sohc --> 5.4 dohc writeups state wiring harness and accessory changes, so they should be the same, and they look externally similar, doing a lot of cross referencing part numbers at work and they seem pretty similar). The difficulty or need for modification involved with the swap is the least of my worries, as I have a ton of car background experience and making parts is nothing new for me (come on, how much aftermarket backing do you think probes have? :rollinglaugh: ). Some of our concerns: 1. The 5.4 makes its 300ci with a greater stroke...which, as opposed to a greater bore, typically does not fare well for high-rpm power. We both really like the huge powerband in the car and don't want to disturb that. 2. adapter plates are a bandaid 3. how will the greater weight of the motor upset the braking and handling balance of the car? we're feeling out a 03-04 IRS swap, so that's a little more weight in the rear, but an iron block is inevitably heavier...as you can tell, roadracing is our priority with this car 4. the 99-04 navigator, which is the most likely donator, is not easy or cheap to find, and is rated at 300/355. Although the cobra r is a perfect example of how heads and a intake can get power out of the motor, we're wondering if it's really worth the trouble if no one has anything but adapter plates. one of the thoughts we had was (being on the trigger for a used KB 2.2 blowzilla anyway) putting our current B heads with a turbo valvetrain on the 5.4 bottom end and putting the KB on top to forget the whole intake manifold deal. would it be a better idea for us just to find a 5.4 bottom end to work with?