the whole 318 thing is the block and shared crank dimensions with the 340. everything else has to be changed or upgraded. this is why people say "why not start with 340 or 360" everything else is there in a 340 for sure. You see these drag race 318s but is the parts combo ever posted? no racers don't share the recipe. I'd venture to say the block with the 318 in the side is the only thing 318. Which brings us back around to the point of how much $$$ is dumped into a 318 vs starting with something else as a base platform? it really comes down to "proving" it can be done and we all know it can, but dollar for dollar is it cost effective and worth it? Traditionally? no but these days where engine cores are drying up maybe...? :)