At 100 psi also, would indicate the return side of the fuel system is blocked. There was a diagnostic step that had us do this if I recall rightly and it remember the gauge tipping around the 100psi mark.
I would think ether hitting that heater would be exciting to say the least.
I've seen it blow intakes and air boxes all to rat shit, so a (likely) corroded all to hell air horn/heater mounting boss isn't likely a stretch.
I like how there's no time for the engine to move oil about on the 6.7 before it ramps right up to 1200. Should be good for longevity in extremely cold environments.
What repairs need cab removal on those? I know brad mentioned fuel system. Is this something the general is endorsing or just like the early fords the techs are making life easier on themselves?
Are you changing the heads? I betcha you got some bent valves.
I would at the very least measure protrusion. I would tell hotline though let them or prior approval decide, or document it well.
You don't wanna marry this shitbox.