Guys, the simple way to tell is to look at the front and rear crank throws. 340s have a hole bored in the end throws to make it possible to balance it with the heavier 340 rods. This crank appears to have the front throw bored, so it's a a pretty good assumption that the rear is as well. Also, I believe all forged 340 cranks were shot peened, so if you look closely at the radii of the journals, you can sometimes see it. I do not know for sure if 318 truck cranks are shot peened. Actually, now that I think about it, I wonder if the 318 trucks had the heavier 340/360 rods as well? Quite frankly, unless you must have absolutely every part be the correct casting/forging #, I'm not sure it matters. If it is a forged, shot peened crank that has the end throws bored and it is is in good shape, run it.