Today, dollar for dollar, is the 318 faster than the 340 ???

IMHO, a waste of money on a well seasoned block that measures out OK.
But it your money to spend to keep from being called a cheapskate.

Some like Budweiser Beer. I would not use it to wash mud off my boots. Basically "Opinions are like ......" My opinions are not always right but maybe some of yours are not too.

If something measures good and in spec, I run it. But I can almost guarantee you are not going to find any Chrysler V8 or slant 6 with a deck surface in spec.