What's the Best Year???

Correct.
I wonder how long a 6.4 would last though if it only had to put under 200 horses down to the wheels.
On a 7.3? Oil pan would be the first thing I look for. They rot out, and the motor must be pulled to replace it. I've seen some cut crossmembers out of the frame to do it, but that's seems dangerous to me.
Look for a forged rod motor. Do some searching around and you can find out which motors had these and which had the PMR's.




