Overtorqued 6.9 head studs are suppling more clamping force than regular 7.3 head bolts, the math doesn’t add up here if you’re having guys pop gaskets at those low of boost numbers yet we’re running in the 20s on stock 7.3s, maybe there’s something wrong done in the assembly like the surfaces not being properly cleaned. The T19 doesn’t have a big clutch option like the 13” south bend we run on the zf5s, like you said most guys making good power are running a five speed because of the better clutch options and cruising rpms. I had a customer in New Mexico running a 130 pump on a 6.9 doing frequent towing and no issues with a drop in turbo upgrade. Both that truck and this stock 7.3 we’re pushing to 300 is intercooled, are any of those 6.9s intercooled? That’s going to make a big difference in intake temp and cylinder pressure. If someone wanted to make big power on a 6.9 a 625 arp stud kit could be put together to increase the clamping force and be pretty close to a studded 7.3. Believe me the 7.3 turbo engines are my preference for reliable IDI power, but I don’t think it’s outside the realm of possibility to build a 300hp 6.9 which was the original question, reliability can be debated but that’s only as good as the quality of the engine build and the parts used.