I expect there are several ways to skin this cat. What's easiest?
First make dang sure you don't have the parts swapped side - to - side.
I rivet them using a rivet gun and bucking bars just like any other rivet.
A couple of hammers do it for me. Those pins don't need much "persuasion" to keep them in place.
That buck bar looks like a slice of a railroad anglebar ... rather inventive.
Correct sir! Cost $0.45 per pound at the scrap metal yard.