Recently I found a fresh water pump on EBay, at rural tractor dealer. The Ford part number in the Lehman parts book was correct,though I think it was an aftermarket part. It is not a Lehman marinizing part. The dealer named a surprising number of vehicles/trucks/tractors it might fit.
The engine was designed/first made in the UK as a Ford Dorset engine. According to someone who used to post here it was unsatisfactory as a truck engine due to wear rates, but a success if the rpm was fairly constant. Being an old engine Ford dealers may not have parts, but as Wxx3 says, American Diesel can help as the effective successors to Lehman.
I bought cooling system parts from fredwarner1, an EBay seller on the West Coast, incl exhaust elbows and heat exchangers and would buy from him again.
Island Gypsy 36 Europa "Doriana"