These sound like the same bolts I am attempting to replace on my Shock Santana. The originals are galvanized steel, 1" diameter x 2.5" length with a tapered head (counter sunk into the keel)
Schock currently uses stainless steel bolts of the same configuration on their new boats. I ordered a complete set of the SS bolts, washers, and nuts. They have not arrived yet but you might want to contact them as they sold me the last ones they had but apparently were getting more from their supplier. They were very inexpensive.