7.3 is pretty bullet proof. Later 6.0's have solved many of the issues the earlier ones had. I have an 03 6.0 the engine was replaced under warranty in 05. Head gaskets have been an issue with many, but there are many that have been trouble free. I replaced the injectors and icp sensor after I bought it in June of this year.
I think the biggest improvement other than power (over the 7.3) is the transmission. Sorry I do not have much experience with the 6.4.
I do know that my 6.0 is a rocket even without the tuner. With the tuner it is just plain crazy.
whys everbody bashing the sicklitres theyr'e putting my kids through college!lolany of the three are ok as long as you know service history and how the vehicle was used,most of the concerns on the sicklitre can be attributed to fuel and driver issues.
a moments silence for the shelbyx,i hope her new owner enjoys as much.
the 6.4 is a leaker too the local dealer has 19 with blown head gaskets and i have 3 comin into my shop they are off waranty already also talked to my buddy in red deer and they have a bunch at dealership there too
thats one reason id never buy a used truck from the west esp alberta (no offence) but working in the oilsands and seeing numerouse trucks run for near a year straight no wonder half of them dont last either its for the heat in the winter not only to keep you warm but keep the truck from freezing or the summer to keep the AC going lol thats alow low k truck like 40/50 thousand with a million running hrs on it outside looks good but motors nearshot not to mention the undercarage.
If I did it again I would buy 7.3, the 6.0 was great for power, but when it ran bad, it was bad. I used to work for International and worked on many of these older engines and they were pretty damn good !!