I have had experience with about a dozen Mopars over the years (Since 1974) with about a dozen 318 daily street drivers. Some where completely stock 2 barrel a few had 340 J heads
and a few with 302 heads. The J heads came on stronger top end,sluggish on the bottom end,302 heads and very strong off idle not as strong as J heads up top. The 318's I had with the 302 and 675 (still have 2) feel stronger and happier as a daily driver where you spend most time under 3000rpm and more mpg. No real A/B tests or dyno. Remember dyno is just a measurement tool above 3000rpm not seat of the pants or dragstrip.