I kind of doubt Ford would have any brand new long block 4.0's in stock. 14 years is a long time.
From the looks of your pistons and cylinder walls I would have no problem just throwing a pair of heads at it and running it indefinitely. There isn't even any carbon buildup, walls have nice cross hatch. If you don't feel like doing the heads yourself, find a shop you trust and have them do it. I'm guessing $3000+, there is a lot of labor involved plus parts. Basing that number off my old boss who had his 5.4 powered F150 in for head gaskets - similar engine there - I believe they charged him about $3500 and the heads were fine, it was actually an oil leak in that case.
I have not done heads on a SOHC engine but from my understanding there is a lot to keep track of with making sure the timing chains are set correctly. Your call if you want to try it yourself - driving it to a shop and driving it out fixed is pretty easy, just costs a lot more.