start with exhaust, a true dual 2.5" system. then look at rear end- posi, gear ratio. I assume your tranny is good- a shift kit and higher stall torque converter will help down the road. Brakes, suspension make sure theyre in top form. THEN I would worry about a motor- a high HP motor will NOT make its best power without the rest of the chassis being optimized for your eventual set up. And yes, the other mods will help out your 305-as well as getting the car ready for a HP motor in the future.