I'd start with 340 100% of the time if cost was no object depends on application if it would be 2.94"/3.31"/3.58"/3.79"/4" stroke. Really if cost was of no concern Aluminum Big Blocks for everything :) Out of 318/360 since the choice for most 360 90% of the time, to me if I wanted to build a light handing manual transmission car that makes medium power 300-350hp but at somewhat higher rpm that I could have fun going through the gears while keep speeds reasonable for the street and sound like a race car 273/318 would be my choice for that. Or if I had a 273/318 car that I didn't overly care about power just a mild cam 4bbl duals and tune would do.
