You mentioned that the 318 would need lots of machine work, what extra machine work would it need over the 340/360's? None. As most guys on here do their own porting. As far as getting 1 horsepower per cubic inch isn't difficult even for the 318.
Take your time and please, explain to me why you would even consider dumping money into machining/building a LA 318 for performance...and I dont care if you go to that Motor Trend article and copy and paste the whole thing ...Ill wait... :popcorn: