Thanks for the reply.
This setup was ran in(1975)my MSV '40 weighing 11,000lbs, light on fuel using the 1.2 overdrive as you stated. The #3 SSM were 1:1 ratio with heavy duty upper-vertical shafts made in Italy. My rolla 4 blade props (I recall) were 26 pitch, 4% to 5% slip. At prop speed max...