I think you are looking for an easy way out. To seal small areas any common sealant will work.
Be forewarned, if your boat has a canvas skin the fiber is cotton which waterborn microbes love to eat. They will go to work on it as soon as you get it wet. If there is any previous microbial damage it will all add fast. The reason for re-skinning with a modern fiber is microbes won't eat the stuff. Plus the age of your hull says the frame should be looked over for safety sake.

: Thanks everyone for all the input and the link to the svenson site! My boat
: looks a lot like "Canvas Back". I think I'll start by trying to
: remove the outer wooden keel. It's screwed into an inner wooden piece and
: some of the screws are backing out a little anyway so I suspect it as one
: source of leaks. Assuming it comes off ok and everything seems sound, what
: sort of sealant would you recommend if I reassemble without re-skinning?
: Silicone? Boatlife? Thanks again.