I have a number stamped on the left side of the engine bay. PU1986. Does anyone know what it is for.

Adam I have one on my bus also . Mine has a DMR prefix from memory, anyway my bus was purchaced new by the DMR as some kind of inspection bus (nine seater) i believe and the number is there for ? service records and or security or something. Perhaps this was comon practice with government Vehicles at the time.
Mitchell