the 7.3 was a great motor for its time, but if you want more options you have to go with the minimum 6.0 and of course the better options and such with the 6.4 and now the new 6.7. As for the reliability of the 6.0, the early 2003 to 2004 6.0 were susceptable to more failures. However, if planned out right and the right add ons and mods, you can have a 6.0 that is a beast, and will take anything you can throw at it. You will hear horror stories about the motors, but keep in mind out of the hundreds of thousand they did sell, how many didnt have a hitch, you arent going to hear about too many owners who had no issues, because why would they ask questions? I have 85K miles on my 6.0 and they only thing I had worked on was an egr failure at 43K miles. Now I do already have a set of ARP Studs, and new MLS gaskets, and oil cooler and egr delete already still in the boxes ready to go just in case it does happen. I found a diesel tech who will put everything in for a good price, and I hear Cody on here is a pretty good diesel tech as well, i dont know about his prices, but when I am ready, I will make sure to look him up. Those motors are like kids so if you take care of them they will flourish. I love my 6.0, as for the newer ones, I cant comment but I love the design of them.