With all used INTL engines, make sure that the coolant has been treated all of the engines life. If not pin holes will form between the cylinder and water jacket at #8 cyl. Its a condition called cavitation.
I have 2 service trucks in the 300's and still going strong.
1 is a 7.3 - 1 is a 6.9. My personal truck is a 95 crew cab 4x4
power stroke, and it has 220k miles on it and seems to run better
check out ford-diesel.com for info on ford diesels
We run 4 plow trucks 2 of which our 7.3 liter. 1 is a 97 Powerstroke f350 4wd get 20mpg city and other is a dual wheel 90 internation diesel 14mpg dual wheels and 10 dump. 4wd and they will run well over 300k if maintained reg