Unless something's mechanically wrong, leave what you have in there. Jimmer, go down the turbo path if you want to, I have 2 turbo foxes, but have the whole plan ready to execute before you tear the car apart. Most turbo projects end with a sold car that's still on blocks. That said, if you have a complete solution before you start, understand the full cost and labor requirement before you get to work, then 500 hp (at crank or tires) is definitely doable.
Some people put a lot of money into a stroker kit, super duper heads/cam/intake etc... The truth with an intercooled turbo car is that at 15psi on pump gas, you can turn a 250 rwhp car into a 500 rwhp car, as long as you have the tune and fuel system to support it. Further, the stock block is never going to be reliable beyond that power level, regardless of the rotating assembly, or block reinforcement. So, when turboing I'm the biggest fan of keeping the H/C/I combo simple and putting your time/effort/money into getting the turbo kit right. Plus, it makes it a lot cheaper to replace the shortblock when it's just the stocker, not anything special.