[Tony Z]

I think the standard advise is always applicatble, strip down the engine. Get the crank counterweighted and all your rotating parts balanced. That should give you a few more revs with less engine damage. While the engine is apart, change the cam for a slightly hotter one. Also, smooth out the inlet and exhaust ports. Put all together and get a decent exhaust.

If you dont want to open the engine, get a decent exhaust.

As for a turbo on a stock engine, well to start, it will work, but... any higher revs will do damage unless you counterweight the crank. If you use the same revs, it will work to a certain extent, also remeber, you will have a cam that is not designed for a turbo, so will loose out on power there too.