I've got a 4" MBRP exhaust on my truck, that was intended for an early powerstroke. you will have to fabricate the part that connects to the downpipe, but the rest works fine. I did have to relocate the front hanger on the frame, but the holes were pre-drilled from the factory so I just moved it back about a foot. Mine's hooked to the downpipe of an ATS turbo kit, and the powerstroke exhaust kit included a 4" to 3" reducer that hooked right up to the downpipe with minimal welding/cutting.
Incidentally, the PSD downpipe that was included in my kit made for a nice intake tube that someone else on the board is now using...
4" is overkill, but the MBRP was cheaper than the Hypermax/ATS/Banks kits that are purpose built for the IDI trucks.
Ryan