EGR has different part numbers on Fender flares between XD and non-XD but I can't figure out what the difference is.
Also the frame is different between the XD and the non-XD so things like BullBars, aftermarket bumpers, tow hitches won't fit.
One nice thing is the mounting brackets for steps that mount to the cab is the same between the 17 and the 04-15 1st Gens, So if you want Step Bars, you can just buy any Titan step bars that mount to the cab (Haven't verified the ones that mount to the frame or the cab mount brackets) but you'll need extra bolts.