That is the kind of detailed explanation that has me lurking so many old posts around here. Thanks and I will ask for that to be checked for sure. I expect a text from the mechanic tonight or tomorrow morning and when it comes I'll ask him about the machine shop inspection.250k to 280k is around where many cams and liters seem to take a dump. While they have been used in other Powerstrokes and other engines, they are highly stressed in this motor due to the spring load and leverage of the rockers.
In both International's and Ford's manuals, part of the inspection process is to check for deflection, warp, or out-of-flat across the widths. I personally think this is where the major issue is, but it's rare to find people who have checked it. And due to Ford's insistence not to machine the heads, what I call "tenting" is never addressed on many head gasket jobs. Which means they will fail later. The gaskets will not achieve full compression at the center of the head if they are not flat.
The other flatness spec, down the length, is not that important to me, although it should not exceed 0.004". Most machine shops look at the length flatness and call them warped but don't check the width; again, to me, the most critical.
A quick check to see if the head has been machined is to check the head thickness. The minimum spec is 3.74" or 95mm. They can be thicker than that, but many find they are at the minimum from the factory.