I culled a 273 crank for use with a 340 setup and I noticed the 273 had THICK wall piston pins, I mean like DIESEL thick, to offset the lighter piston weight, I guess so they could use a 318 crank without Swiss-cheesing the counterweights!!! Couldn't really tell the difference in it and a '68 LA 318 crank, both using the skinny beam rods.