I don't have specific information on the engines in question, but Chevy made quite a few marine engines for different companies. My Tonawanda production totals showing engines shipped to Kiekhaefer as of 7/17/69 are:
3951055 normal rotation: 1200
3951056 opposite rotation: 176
It also lists:
3962652 Hi-Perf normal rotation: 1
I have no idea what these engines consisted of. Maybe someone can find references by part numbers.
Verne
For added interest, here's a twin turbo version shipped to Daytona Marine.