Rivet Question

[Super88]

While replacing the rear header on my 1930 Tudor, the right side corner bracket that attaches to the rear roof panel came off. It was held to the roof panel by one rivet that appears to have the "waffle" pattern on the end.

Considering the small amount of room, how was this rivet set? Since it will never be seen again once the car is completed, would it just be easier to replace the rivet with a nut and bolt?