Which 318 should I build ?

aren't the 4 bolt mount 318's from the later 60's the best blocks? They "say" you can bore them out to a 340 and put 340 pistons in them, though I've not tried it. I did have a 4 bolt mount block recently and I gave it to a mopar buddy.
I have heard that some can be bored that far but I have never seen one.