If the 46 is running the original cooling system, it's a "zero-pressure" system. As long as the cracked area of the block is cleaned thoroughly, a coat of "Marine Tex" over the crack and an inch or so beyond it in all directions, it should contain any leaks. If you press a piece of 40 grit sandpaper over the repair as it's curing, the texture of the patch will be almost exactly like the surrounding cast iron.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!