I recently replaced a length of toerail just like yours on my 1993 First
310; the original rivets are apparently custom, looks like old-style hold-the-receiver-in-place-and-hammer-the-rivet-in, not a pop rivet style so no center hole. Luckily, the area I had
to replace at the bow was open underneath the rail inside the anchor
locker, so I could get to the underside of the rivets. It was easy
enough to find stainless bolts, nuts and washers to replace the failed
rivets without changing the look too much, and actually made it easier
to place and maneuver the new toerail into alignment. Good luck!
P.S. I still have about 20' of the toerail that I'd be happy to send to anyone in need...
-Phil