I have a new box of tapered cast iron screws and the unused drill and tap to go with them but once I used Marine Tex I never sewed another block. I blast with media, gouge out a shallow "V" groove the length of the crack, rough on both sides with 24 grit and smear on Marine Tex to maybe an inch on each side of the crack. Never had one fail yet. Picture is of a 1940 Pontiac 6 cylinder block where the crack runs into a freeze plug hole. Used a rubber freeze plug which will seal a slightly irregular surface which the hole had after patching. That was 5 years ago and not a trace of a rust trail around the patch yet.

http://s32.photobucket.com/user/coilover/media/40%20Pontiac%20engineand%20trans%20002.jpg.html

Evan