Every hydrocarbon burns in two steps, the first is hydrogen oxidation, making water vapor and the second is the oxidation of carbon yielding carbon dioxide. That first oxidation is the hotter of the two. If the engine is blowing smoke, there CAN be excessive exhaust gas temperature.
Direct injected engines, of which the multifuel is, have hottest temperature in the piston. Naturally, the pistons are cooled with oil jets BUT looking at the spherical combustion chamber, there is a long distance from piston crown to the oil jet cooling site, meaning that bowl top and piston crown WILL get MUCH hotter. Guess which part of the piston is most critical with respect ring load? The crown. This is why most DI diesel pistons have steel top ring inserts. Still, getting the crown near the melting point means the aluminum turns into something like bubble gum.
Indirect injected engines are different, heat is concentrated in the head BUT pistons still can be overheated. You may get away with huge power in a diesel engine for a few seconds. Not in a 50 year old design. Modern pistons have far better cooling, many have oil jet passages for crown cooling. So don't think you can make this engine anywhere near the specific output of a 6BT Cummins.