The recommended range for the stock set up is between 400-450 rwhp depending on the tune and driving style. Some people have had 500rwhp cars that hold together for quite a while. Others blew up at 390 rwhp driving like retards.
The block is good to over 1000 hp
The stock crank is not recommended over 600-700 hp
The stock rods and pistons are crap and can't take more than about 400-450 hence the limit.
The heads don't flow well enough to approach the limit without a power adder, the n/a aftermarket is too expensive to make it work.