Need help to identify this isx...

[DieselKid]

Depends on the repair. A recon engine carries it's own ESN and is complete engine, ie block, head, internals, peripherals like air comp manifolds turbo harness etc.
Hard to tell why there is a long block in that chassis with out more info. If you can supply the vin I can check warranty history to see if the long block was supplied as a warrantable failure repair.
What do you mean by million mile plus block?