You've found the problem on the ranger, the AC air box sits right where the turbo wants to go. The only way around this is to relocate the turbo. The guy selling the header for $250, his name isn't Bob is it? If so thats supposed to be a great header and a very good price (I'm not sure how he does it, I'd have that much tied up in materials). That is actually a "weld el" manifold which is a thick cast steel. Its becoming popular for all aftermarket turbo setups because its cheap and its strong.

If this isn't it, give me a link to what you're talking about, I'm curious what they are doing.

Redoing the intercooler plumbing isn't a problem at all, we just may have to cut a hole in the core support (not sure what kind of room there is in one).