Some how we have gotten to the point where guys making 600 real HP (as the OP says he is) don't think they need an aftermarket block. Not only is reliabilty down using P car blocks so is your HP. Your tune up window is significantly reduced, so a minor tuning error will cost you big time.

If you can't afford/want an aftermarket block, think about a reduction in HP and RPM. What you are using was never designed to have done to it what you are doing. All the tricks in the world won't help that.