i judt looked up the the heads online. it looks like the going price for the X heads is $1300. thats a little steep for me considering that will pretty much double the price of The build. im looking in the 400-650 range
To get 300 plus HP in a 318 you will need a good head. At least 1.88 valves, but 2.02 would work better. Maybe you should just stick to bolt ons like carb, intake and headers.