Clamp screw, swivel plate

[ezeb1473]

I have two engines each missing the swivel plate/retainer on 1 of the clamp screws. I got a new swivel plate and the retainer clip but not sure how to keep the retainer from from falling off. The other side looks like the retainer is peened over but not sure if nor how to do it.
Thanks
Ed

[boats.net]

It's like a brad rivet, have to flare out end of screw with hammer and punch.