That skunk 2 intake manifold you have will come in handy if you get cams, otherwise it really isn't doing much. I say x2 on the exhaust. I would wait on an ecu until you have alot of the parts you plan on getting, and I'd go with a Phearable basemap ecu.
first of all with just internals, you are going to need new pistons, probably ITR or P30 pistons, and then clay your motor to make sure the valves are cool. Then degree in a 403 cam or a 404 cam and add supporting mods. THEN its a gamble as to how much HP you gain. IMO its nor worth it..