I've put in stainless rivets. The hardware is stainless and the mast is aluminum. I put some lock-tight on the rivets to help stop the oxidation. Not sure where the oxidation was going on before. Seemed like it was just very old.
A new problem is pulling the rivets. pneumatic puller that are reasonably priced can only do aluminum and up to 90 pounds. These take a ton more force. I would guess around 300 pounds or so to have it pop. I used a carpenters clamp to help provide the power. I've also used a large table vice that is not mounted on the table. Really slow process. I may have bent the puller in the process. Can't seem to get good purchase on the rivet. I squeeze it down and it doesn't make any progress.
My other problem is figuring out how to mount oarlocks. I don't have money for motor right now and I want to row it anyway. I've never worked with fiberglass. Is it possible to drill it without cracks? Is it possible to cut?