One simple thing(among many) that separates 1HZ, 1HD-T, 1HD-FT, 1HD-FTE and highlights the potential for power is fuel injection pressures.
From memory, so don't quote me
1hz injects fuel at 1900ish psi.
1HD-FTE roughly double the HD-T (can't remember a number)...
I've seen it talked about lots on forums, not sure I've seen anyone follow it through.
I don't think there's a direct bolt in solution without changing timing case and gears?
I think cost of parts would mean it doesn't make much sense.
So some searching in this forum.
Why upgrade the power? Why not. You could argue that utilising the engine's inherent potential with an increase in torque and power output means the engine is not labouring as hard as a less tuned and optimised engine.
The HD series of engines were used as...