Is this a cast or forged crank?
OK, I'm gonna stick my neck out and still say the bottom one is cast. Note that the center counterweight is significantly smaller. Also, the rod bearing widths are narrower. I'm not aware of any slant six forged cranks with a smaller center counterweight or smaller rod bearing widths (of course, I have been wrong before). Here's a pic that Dutra posted on Slant Six Org. a few years ago, when he was putting together an aluminum block slant six with a cast crank. Looks to me like the bottom crank above, albeit ground on (lightened) a bit:
Another:
OK, I'm gonna stick my neck out and still say the bottom one is cast. Note that the center counterweight is significantly smaller. Also, the rod bearing widths are narrower. I'm not aware of any slant six forged cranks with a smaller center counterweight or smaller rod bearing widths (of course, I have been wrong before). Here's a pic that Dutra posted on Slant Six Org. a few years ago, when he was putting together an aluminum block slant six with a cast crank. Looks to me like the bottom crank above, albeit ground on (lightened) a bit:
Another:
