Jeff,
Glad Mr. G's worked out for you.
However, on a going forward basis, you might consider a 1959 Cadillac Master Parts Book.
In there you will find a description of just about every screw, nut, bolt, etc used to build the car and diagrams of each of them for naming (Fillister head screws, thanks Grant) along with: sizing - TPI - zinc - cadmium- chrome etc.
Have fun,
Steve B.