If money is not a huge factor I would bore and stroke the 318 to 390 and change the cylinder heads with 5 axis ported ones from Indy Cylinder Heads. A cam shaft from Lunati and a stroker kit from Muscle Motors, RPM Machine (I have theirs), or 440 Source, ect. and 400 horsepower will be easily achieved as well as a lighter wallet and bank acount. Now you will need to upgrade the stock exhaust manifold with TTI exhaust headers and system (3" x pipe on mine) as well as your brakes.