A 300 plus HP 318 is not an impossible objective, overbore it, 0 deck the block, add a good cam and a 4 barrel with a good intake (like the Edelbrock RPM Air gap) , a dual 2 1/2" exhaust system and you should be in the ball park. You can go fancier by reworking the heads and some more extras but they are not really necessary I think. You don't even have to change the bottom end unless you get into drag racing or have a healthy budget.