I have a 1999 with the 5.4 engine that is about wore out. I have located a 2009 5.4 with 400 miles that I can get really reasonable. What issues would I run into trying to install the 2009 into my 1999 or is it even possible?

 

You can get it in there, but it won't work.

You need a two valve, - 4.6l, 5.4l or V10.

 

You would be better to replace with a 5.4 and then supercharge if you are looking for more power.

 

Putting a 3 valve engine in would be a major undertaking. You are best off sticking with a 2 valve - if you want something newer than a 03 engine look for one in a wrecked E-van.

 

What ever money you'll save from buying the engine will be more then spent modding your truck and the engine to make them compatible. Get your 2v rebuilt or try to find a nice low miles used one. That will save you way more in the long haul.