Not aware of any site where someone (or many) have taken the time to study and post (after surely thousands of hours) all the head markings by plant and production period for the Mustang. Most of the time these efforts spring out of an individuals need so this might be your opportunity
Might be able to get a site up in five or so years
AMK tends to focus on the size and thread of the original hardware as well as original finish when possible (not every bolt is in production right now) if the head markings happen to match the original design he got lucky. Most of the time IMHO it only happens about 30% of the time for San Jose cars - and not every bolt and piece of hardware is being produced.
Best source is a parts or donor car from the same plant and time. Its always surprised me that Mustanger's and those restoring cars from the 60-70's rarely purchase a parts car for their restoration where that was a common practice of those restoring the 30-50's cars. When our cars were plentiful in yards we would typically take a day and strip on or two cars of all the bolts we could before any trip to the platters than pick through the plated stuff, choose the best for your project and either save or sell the rest to another.
