Have you tried Spare time Shop in Marlborough: The SPARE TIME SHOP - Models, Hobbies, Games, Rockets, Trains, R/C, Slot Cars, Magazines, Books, Pre-built
I've had good luck with Scalehobbyist: Scalehobbyist.com: Model airplanes, ships, military vehicles and modeling supplies, and i know other people have had good luck with Model Roundup (but I haven't used them myself): www.modelroundup.com
I believe the engine is a Cummins NHC250 (generally painted a sandy beige color from the factory). I don't see why the turbo wouldn't fit under the hood. I guess the only way to be certain is to assemble the turbo engine & see if it fits.