That is impossible to say for sure. I would say it would depend how you drive it and how the tune is. I have read about blocks handling more that 600hp with good tune but with anywhere near that much power your going to break something sometime. I would recommend if your going to build a stroker motor, get a stronger block so that you don't have to worry about replacing it all if it splits a block.
You can find a Mexican block for around $300.
You may be lucky and never have a problem but why take the chance.
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James Cox
nochevy@hotmail.com
1991 Mustang LX