Original Prime Mover?

Yesterday I saw a BNSF SD70MAC that was built in 1996. Is there any chance that it has the original prime mover? If so I would imagine it's been rebuilt a few times. Or has it probably been replaced?

Some years ago I travelled over to Topeka and the BNSF (née ATSF) shops there. There I saw, on a SD70 frame (the Grinstein Green cab was intact), a 16-710 block. It looked as though it had been stripped.

I believe BNSF does overhaul their 710s, rather than buying completely new prime movers.

That makes sense. I wonder what an engine costs. I am guessing around $250K.

Nobody buys a new engine when there are so many used yet serviceable blocks available. It's the most valuable single component in a scrapped locomotive.

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"Trains" ran a several (three?) part article on the basics of diesel locomotive technology, back in the 1970s. At that time the rough estimate was that, by cost, a diesel-electric was about one third the Diesel engine, one third the electrical stuff, and one third everything else. Since a new (main line) locomotive these days will set you back. ??? maybe three million dollars? my guess would be that a new engine (assuming the builder was willing to sell you one) would be about a million.
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But, also from ancient history... periodic overhaul of the engine and of the rest of the locomotive didn't take the same amount of time. So railroads with large fleets, when a locomotive came in for a major overhaul, would remove the engine and deal with it and the rest separately: when it was time to put an overhauled locomotive back in service, they would install an available engine (one the same sort), which might not be the one that had come out of the locomotive at the beginning of the overhaul. I believe the New York Central had this policy for locomotives with 1600 hp Alco 12-244 engines (so: FA-2, RS-3) since they had a couple of hundred. On the other hand, the NYC had only a handful (7? 9?) of locomotives with 12-251 engines (RS-11), so this system was not set up for them: when an RS-11 came due for overhaul, if the rest of the unit was done before the engine, it would just stand, engineless, until the original engine was ready for re-installation. (And, no, I don't remember where I read that. My source talked about the Alcos: I assume that the procedure would have been the same for the hundreds of units with 16-567 engines.)

Addendum. I have seen a photo of a retired F-3 or F-7 booster unit that some railroad (C&O?) used as a company service freight car, for shipping 567 engines from one workshop to another. (Makes sense: you don't want to damage something as expensive as a locomotive Diesel engine by having it improperly supported in shipment, and the retired locomotive would have appropriately placed mounting pads.) But look what this presupposes: there would be no need to transport engines separately from the locomotives in which they are installed unless engine overhauls were done at a separate location from general work on the rest of the locomotive. Which I think would increase the likelihood that engines would be switched from one locomotive to another.

And I think GE had a "unit replacement" system for FDL engines: a railroad would ship the engine to GE for rebuild, and GE would provide a new or newly rebuilt engine to replace it. So GE locomotives on railroads participating in this program might go through several engine blocks before retirement: all, perhaps, originally made about the same time as the locomotive's construction, but removed and sent for factory overhaul at different times.