I'm guessing it's expensive because someone told him the block was special with no engine number. His claim is incorrect though. All NASCO new blocks whether for boats, cars or fork lifts were sold without engine numbers. If the motor was to go in a car then the owner was supposed to drop into the local cop shop to get it stamped (hence the VP and NP etc blocks)
Lots of owners didn't bother.
I don't think there was a requirement for boats or fork lifts to get a number stamped, though I am not really sure on that detail.
Ken