Yes, these will fit that engine block & even come fitted with EGR if you choose to keep it. Either reuse the stock header gaskets or just buy a new stock set from the dealer.....don't waste your time with the ones that come in the box.foreverfalcon40 wrote:Any GMT800 style headers will fit, no special swap headers?bai78 wrote:http://www.ebay.com/itm/ws/eBayISAPI.dl ... OU:US:1123
These are the ones I'm putting on my 6.0. I can't say how the fitament or clearance would be in a GMT400 body/frame though.
Double check the header bolts & see if any are snapped off. That's a normal issue with the Gen III.