3306 pre combustion , operate at low speed?

Anybody have any thoughts on running a 3306 pcta engine as a 900 rpm power plant,
I have several 3306 s, and some 1800 rpm gen heads, my thoughts are to overdrive the gen at 2 to 1 and hopefully get decent fuel consumption, the predecessors to these engines ran pretty slow so I hope that if I play with the timing a bit , and find a suitable turbo ,maybe I can get good economy and life from these engines?

The 3306 was never designed to work at such low speeds and the actual fuel burned per horsepower produced at the lower end of the speed range is greater than that between around 1500 to 1900 rpm. It will cost a lot to find a suitable step-up gear and make the conversion and it will repay you with shortened engine life because much of that extra fuel 'burned' will finish up as soot in the crankcase oil.
I have experience of a Cat 3408 marine engine which was often worked around 950 RPM, and when a smaller propeller was fitted to bring working speed up to around 1100rpm, life between overhauls nearly doubled and it burned two tons less fuel per fishing trip, and this was a 1400 rpm unit.