Performance from a stock motor is mostly about tuning. Make sure your ignition system is in good shape (including the timing belt) and that you have a fresh fuel filter and good fuel pressure. There are things you can do to improve a stock looking motor internally such as camshaft, larger bore, valve work, etc. Or you could go "mostly stock" and add a header, and an "Offenhauser" intake manifold for a 4 barrel carb (they pop up on e-bay pretty often). There's also a neat dual 2 barrel side draft setup ( like the racer walsh setup) that will set you back about $850. Just some options.

Chuck