Depends on how you build and what you're going to do with the engine. The Purpose of an intercooler is to Cool the air coming off the turbo and ultimately keep you EGT's in check. Now this is an extreme case but this guy is ~1,200 HP without an intercooler.
http://www.trucktrend.com/cool-truck...s-race-engine/It very much depends on the function of the truck. If your going to do mild tuning and run it down the road you'll be fine without an intercooler. Just get a Pyro Gauge and keep it off the ~1200-1400F for any kind of duration or you'll melt stuff. I have an interccooler on mine and i can hardly get it past 1000F if i BEAT on it.