Since you have a "new" engine with a "new" crankshaft, I would look in an expanding search for the problem. I'm assuming you are using the harmonic balancer that came with the engine swap.

Could one of the driven auxilliary pulleys be so eccentric that it is setting up a vibration that killed the new pins?

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)