Thanks for the reply, P8dawg - I was beginning to wonder if I was just talking to myself! Last weekend I did remove and re-caulk the starboard chainplate and the nearest stanchion, as well as the stanchion next to the port chainplate. I didn't get to the port chainplate due to lack of time, and the fact that it looks like I'll have to remove some wood trim in the head closet in order to get at one of the nuts.
I'll be doing some more work on the boat tomorrow and we've had some rain this week, so I'm going to keep my fingers crossed that I took care of the problem and the toerail isn't really leaking. I couldn't tell for certain and knew that the chainplate and stanchions were definitely leaking, and I also felt some wetness in the fabric over one of the toerail nuts. However, I couldn't tell if the water was just travelling or if the toerail nut was really leaking. I've also got some kind of a leak over the quarter-berth but haven't yet identified what that problem is.
Ah, the joys of owning a nearly thirty year old boat! I have a May 9th launch date so I'm looking forward to getting in the water for the first time.