Mmmm, I think the point of the discussion has been lost.
I have to agree with the OP, at least somewhat. Dollar for dollar, the 318 is a smarter choice. And for two reasons:
1. You can throw the same parts and work at both engines. The difference is the overhead. The 'gateway' fee. $2,000 spent on either, you're looking at a running 'core' 340, or a reasonably stout 318.
2. The stigma of "it's a 340". If you were building both engines side by side, even if you got them both for free, odds are more money will still go into the 340 because "it's a 340". Therefore it gets the good stuff. 318's are plentiful enough to where building one can be a very budget-friendly and guilt-free experience. Chinesium intake and cam? Maybe heads? Sure, who cares, it's a 318. Uncle Richards AFB that's suffered more *percussive maintenence* than any of us did growing up because he still has to get around to sorting it out (he won't), absolutely! "It's just a 318." I feel you would see FAR more backlash for putting cheap parts into a 340 than ANY manner of 318 building.
Just as an example, I am building one with a 60's marine 4-barrel + AFB, (intake bolt-hole redrilled) 5.2 magnum heads, 273 manifolds, old dual-point hemi dizzy I cobbled together out of parts, and a VERY mild cam. Total cost: <$800. And it will do absolutely everything I want it to do.