Ted,
I replaced all of mine last year with the Schaefer stainless halyard exit plates. Some are flat backed, and some have a slight angle back. If I remember I needed two with the curve and 3 with the flat backing. They are about 20 bucks each or so. They look great and will not pop out like the old brittle plastic ones did. I sealed and rivited them to the mast, and they fit perfectly over the old holes.
Also, 2 gallons of bottom paint should be more than enough. (from you other post.) I usually buy 1 gallon and 2 quarts as mentioned by others as well. I use Petit Horizons multi-season ablaitive paint and over coat every year.
Regards,
Todd