No, actually the zinc and the cadmium to most people are really going to look the same. They are both silver in color. To me, its a very subtle color difference.
As for the correct style fender bolts Im not sure if we can really figure that one out 100%. We can look at the different styles that were available on existing original cars during that time period, but I would think you are going to have variations from day to day and hour to hour. Ford had multiple vendors for this hardware and for them it made no difference which one to use as long as it was the correct bolt for that application. At best we can get a general idea here.