Fordged 318-3 truck crank or Poly crank, need help ID

I just bought this because its forged and its supposed to be the 340 stroke and supposed to fit an LA. And I suppose that whatever is up with the rear flange I can make it work as long as the crank will bolt into a block. Thats alot of supposes, but who can argue with the price. Course I havent actually gotten it to my door either.

The way I want to use this crank is in a siamese 340 block. Some super lightweight pistons in a natural aspirated engine with some decent rods. Try to get the bobweight down as much as possible. With the balance Ill hope to find a machine shop that can turn the outmost parts of the counterweights down to get most of the balance in check then finish it with drilling. Or possibly even some heavy metals to allow the counterweights to be cut down even more. In other words, try to make a superlight rotating assembly with as much weight as close to the centerline of the crank as possible. At least thats the plan. May be a few years before that happens though, but by that time these cranks will really be hard to find for a good price. So I went ahead and got it.