Rivets and associated tools have been discussed a lot. Try the "search".
From what I've determined, Ford, and its suppliers, used industry standard rivets. Your best technique to find a specific rivet is to use a
dial caliper and measure certain rivet criteria and match your measurements to a rivet supplier.
I use "jay-cee sales and rivet inc" -
https://rivetsinstock.com/ The critical dimensions and characteristics are:
head diameter (to determine the top die);
head height (also to determine the top die);
rivet diameter (you usually have to drill out the existing rivet to determine this with the dial calipers);
grip range (this is your "length", in other words, the thickness of what you want to rivet together falls in a "range", and the rolled over bottom is usually included in the "range");
rivet type (most of the typed found in Mustangs are "semi-tubular", they have an indent in the bottom for a dimple on the die to engage with. There are solid and pop-rivets also used);
material (mostly aluminum types were used for the smaller applications, a magnet helps);
finish (usually is a bare aluminum rivet, sometimes painted; some are dark and are steel);
Jim
The above link sells the rivet tool and dies. There are others.
