Hi David. Older boats of this genre rarely came with much more than 3-ring binders full of manuals for installed equipment, virtually nothing on the boat itself. Even where a wiring diagram was included, they are usually woefully out of date due to subsequent changes that went undocumented.
As a bit of background, these boats, while more or less production boats, were not built in factory-like processes. They were usually built to a brokers specification and varied quite a bit. Documenting the build, including variances from original specs, would not have been high on the list of the non-English speaking project manager.
The good news is you have found an excellent source of information in this forum.
1970 Willard 36 Sedan Trawler