340's were one of the few motors produced strictly for performance. They didn't produce them in any other version. '67-8-9 Z28 302's also come to mind.
A Chevy 302 is basically a parts bin engine. It's a 327 block with a 283 crank with an old 327 fuelie cam. They weren't all that special, just a good mix of parts and some redesigned pistons.
340's are a different story. It doesn't share many 273 parts, it was a major redesign. The 340 TA 6-pack motors were the pinnacle.
