Normally, you would drill out the rivet, then replace it with a slightly longer one if you were going to place a washer between the truck and frame.
You can tighten up the rivet by tapping very lightly or if you have a press, using that.
Be careful not to make the rivet too tight, it will bind the trucks' movement.
(learned the hard way)
If rivets are not available, I have used small nuts and bolts to attach trucks to frames, using a dab of loctite on the nut.
Happy Rails.
Dave