I’ve got lots of 340s apart. I can’t say that I have ever looked for the number on the forging on a 340. I've got a real TA motor apart right now and can look for a number. There is no difference in the part number, as stated several times, in all forged 340 cranks. All 340 cranks had the rod journal end drilled to remove weight for balancing. All 273 and 318-3 steel cranks did not have the journal drilled. It is solid. Therefore it changes the balance. 273 and 318-3 used the same steel crank. The 273 used a very thick wall piston pin to make the balance work for the same crank. My understanding is that all the counter weight throws were the same on all 273-340 steel cranks. Sadly, that crank looks rusted beyond use. It’s not a special crank.