So... What did I buy?

4spdragtop said

Looks like forged crank. Where's the weird block #'s? In 5th pic I see "JM 340P". Nothing on vin rail?
340-6 stamping is normal. The numbers following the dash usually range from 1-8. I've never seen a dbl digit there.

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Most all blocks higher then 340-8 were garbage but there were some that passed QC and made it out the door. I have seen as high as 13 but over 10 is very rare. Race blocks went higher due to high nickle content making the end of the ladle more stable and hot.

The block the OP has pictured is not a T/A block the main webbing is to thin at the rails . Here is what the webbing of a T/A looks like which accepts 4 bolt mains Look at the width at the rail compared