340ci vs 360ci engine

An interesting comparison is between the 73 340 Dusters and the 74 360 Dusters. Comparing the earlier much less emission controlled high compression 340's is not really apples to apples. What you will find is that the 360 made more HP according to Chrysler.

Car Craft ran a 14.6 at 95 mph 1/4 mile with an auto and 3.55 gears with a 74 360 Duster.
Road Test magazine only got a 14.56 at 96 with the higher compression 71 Demon 340 auto.

Basically it's not really about the block, it's the heads, compression, cam, etc. All else being the same the extra cubes of the 360 will give more power. It's like adding a small stroker to the 340. The 340 can take a bigger overbore but so can the 360 blocks of the same years. It's also the same argument when comparing building a 273 or a 318. The 273 was seen as a performance motor from the factory but the 318 is a much better starting point for a build in the aftermarket.