UUUps...an NSX engine blowed up ??
I have heard about that 2 times over the last ten years.
The only statement for that (if it wasnt a material fault )is:
Could it be that you drived with too less oil in the engine ?
The connecting rod bearings will be damaged soon if this happened.
If you open the engine you can take measurement and surely
you can see the tracks for that on other bearings too.
Its an creeping damage and if this happened you can be sure that after some thousand miles latest, the engine shows his inwards.
(Mostly with full throttle)
Could that be ?
Hope that you find a good used one.
But it will be difficult.
If I would need to buy an NSX engine, I would remove the oil pan and remove one of the lower connecting rods for an detailed measurement. If there are scratches inside you can see or feel, let it be.