Nice looking car.
Hate to throw cold water on this, but even if you find the previous owner you may still hit a dead end. If the PO wasn’t the one who originally built the car, he may not know any more about it than you do.
The guy I bought my 68 Valiant from was one of those people (nothing against anyone by the way). He bought the car about a year before I bought it from him, raced it a couple of times and put it up for sale. Basically, he was just going by what the guy he bought it from had told him. There were a lot of things about the car he just didn’t know about (if he had I’m sure they would have been listed in his ad). I bought the car to re-motor and those things I was mostly concerned about (body and suspension) were easily inspected before I bought it. Unless the car was local, even knowing things like the machine shop and builder that did the engine for instance really doesn’t matter unless you can get a feel for the quality of work they do. Chances are if they are a busy shop that they won’t remember the job anyway, (but they might have a copy of the invoice of the work they did or parts that were used).
Frankly even if I knew a particular car very well (i.e. if it belonged to a customer) chances are I would either cross my fingers and drive the wheels off of it, or spring for a gasket set and do a tear down and inspection.
Anyway, good luck and like I said nice car.