Today, dollar for dollar, is the 318 faster than the 340 ???
Believe what you want, 4" bore is not "magic".
Yes it is. Think about it - The 1970 Trans Am cars were running de-stroked 340's (4" bore!) and probably made 600+ hp. Why dispute facts and reason? Why bother with this kind of nonsense you see below? Those fly cuts in the pistons are almost laughable. If you're already going to spend money on "better" parts to hop the thing up, do it right, skip the 318 and go straight to the 360.
As most here are probably aware, that pic is from that "Junkyard Jewel" article that Steve Dulcich wrote like 100 years ago. Read it, it says essentially the same things I say in my post. No matter though, some people still hold it up to be the Tabula rasa of cheapskate Mopar engine building. If it's so easy why don't you see 400hp 318's al over the place?
318 Small Block Build - How To - Hot Rod Magazine
In all the years since that article was written, I have yet to see anyone step up and duplicate the recipe, probably because A) it's not that easy and B) most guys realize it's not worth the effort and expense just to prove a point. I think most guys miss the crux of the biscuit anyway, he's not just bolting **** together and saying it makes 400 hp which was probably a stretch anyway.
But hey, if that's what you want, go for it! Do all the same **** he did, use the same parts (like you say, use the best factory heads!) and methods. Prove it to everyone it can be done. Take it to a dyno and tell us the number then put it in a car and take to the track and see what times it runs in real-world circumstances.
318s are good boat anchors but that's about it.