Outsider, the folks at MP are no dummies. The Product Marketing people (read advertising guys) certainly understood the benefit of selling "340" blocks instead "360" blocks to Mopar guys.It's more of a Marketing thing. Fact is, everyone bores and strokes everything anyway. Why not ride the free adverstising coatails of the Legendary 340? What small block Chrysler evokes more passion than a 340? They could have called it the SLAB " Super L A Block" but it just wouldn't have the same ring to it! You'll sell more $$ worth of parts! Why do you think they brought back the HEMI and pasted it all over both cars and trucks? Marketing, pure and simple. All things being equal (compression, cam, valves, heads,etc.) the 360's 20 more inches would have the advantage(albeit slim)over the 340. It's moving more combustable fuel/air and thus should create more energy.