Wow that 2000 pound payload seems a little optimistic.View attachment 91202 Long before the Seawind there was the Porschel Equator P-300 (recip). Developements like the turbine powered P-400 did away with the drivelines and gearboxes to the prop.
Its in the December 1971 issue of Private Pilot Magazine. Wish I could get a better pic to post, but hopefully this Wiki link will fill in enough details.
Every bit helps !