I'm unaware of the cost of a reman s60. So I cannot say weather it would be cost effective for him or not. I can drop a reman 6nz rated at 550 in my truck with the warranty for $36000. Used with 600-700k about $8500-9000 depending. Even swapping a used s60 with 600k on it is a better option than running this truck into the ground until the motor finally quits. If he gets 300k out of it and saves his down time and runs it 3 years he can afford to overhaul the motor if he puts .10 in an account over that 300k
That's just an option he can think about like I said I know more about cats than I know about Detroit's. Never figured they'd be worth an arm and a leg though. I suppose its like the 6nz with the glider market though. Most I see that have a motor say 12.7 or 6nz in the description.