I built one to about that spec for under £200, its running in Marts escort now. worth the cash if you've got no mechanical nouse, but its not rocket science to build one yourself for little money.
If the 'low comp' pistons are std skimmed ones, you wont be able to run over a bar of boost without them melting too IMO. If they are proper forged ones its a fuckin bargain, buy it now