I haven't seen anybody build a naturally aspirated Duratec 2.3 in a Ranger. The Duratec Ranger performance aftermarket is pretty much limited to a shorty header (the factory manifold looks really good though, so minimal gains if any for the header), cams, an underdrive crank pulley, or cylinder head upgrades. And of course you can always tune them to using an aftermarket tuner. Anything else will require custom fabrication.
There are a couple of very nice turbocharged builds on TurboRangerForums. ONe is a remote setup, and the other is full of custom machining/fab and runs 10s in the 1/4mile.
You could always look at NC Miata builds since it's the same basic architecture, and the Duratec/MZR 4 cylinders are popular swaps into Locost builds too due to the hp/weight.
Moral of the story, is there are plenty of examples of things that can be done to the Duratec 4 cylinders, but almost no examples specifically in a Ranger. You'll have to do some research and decide what you think would be worthwhile/applicable for your truck.