I'm at $38.5K +/- $3.6k/$4.7k depending on pictures.
My honest answer is close to $40k.
If you said the engine had 40k mi on it, I would give the engine no value outside of the car. At 4k mi, that $15-20k expense isn't amortized yet. No, he can't get the cost of the engine build out of it, but he can get half.