Don't tap the holes! If the bolt turns into the block hard, run a 1/2"-13 DIE over the eye bolt threads. Sometimes just cleaning up the threads on a wire wheel buffer is all that's needed to smooth out the threads. Be sure the eye bolt is a forged item, not a simple rolled type, or be sure to weld the eye into a full circle. I've seen low-strength rolled eyes straighten out and drop an engine- - - -not a good idea!
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!