My uncle use to put his built 340 parts on 318 shorts in between 340 builds it was obviously a notice different cause of cid and cr but worked very well with heavily ported TA heads large solid cam etc,, and years later when my cousin brought the 70 Duster back to life we did similar to it and had lot of fun with that, It's been sitting without and engine for quite a while now, been trying to talk them into getting back on the road. The 318's I've had been more mild, 340 cam 360 heads and intake they ran good.
Ask the guy with the magazine 477 hp 323 he's on here.