The block guard doesn't do anything. If the cylinder is going to crack, it will crack, regardless of whether a block guard is run or not. The longetivity of the motor is highly dependent on how good the tune is.
I wouldn't go as far as sleeving the motor (since I have seen over 600 whp on stock sleeves), but it would be a good idea to think about some forged pistons, forged rods, and some stronger rod bolts.
I don't have any 1/4 miles times...yet, but thanks for looking.