First of all, Lehman is strictly the marinizing company, as is ADC. The engines are actually Ford. And an ADC Ford is not a Lehman Ford, even though they share some basic features.
So, I guess it depends on what information you are looking for. While Bob or his son (I forget his name) can tell you the difference between Lehman and ADC, they should also be able to point you to where to get the info directly from Ford.
I'm shocked that Bob wouldn't have one. Sure you talked to the right company?
I'm sure he or his son can get one to you, or at least point you in the right direction.
There is also one more possibility. Marine Trading International of New Jersey installed these in a number of their IT40 and IT46 Island Traders in the late 80's and early 90's. Their phone number is 732.286.4000. They may have one, or at least a line on how to get you one.
My manual is currently on our boat at a yacht brokerage in Seattle (I'm in Port Angeles) or I could photocopy it and send you a copy.