They only thing I've ever seen legit on those type kits is the manifold and turbo. For a stock 2.3/2.5 you would have to tap a hole in the side of the block for the oil line to the turbo. Also you can't run much boost with stock pistons (too high of compression ratio). To add a turbo to the 2.3/2.5 you just about have to build it up or swap in a mid 80s 2.3 from an SVO mustang, tbird, merkur xr4ti, and i think there was a cougar that had one.
Check out this site for more info:
The guy that started it is legit. I think he had his truck running low 13s high 12s in the quarter. He built his engine with about 3000 dollars. But there are so many how to's on that sight that you can't go wrong.
NOTE that kit is most likely for the SOHC Rangers not the Duratec DOHC