Glad to hear you passed on the truck. One thing I want to point out, even though I am sure you are aware, is these trucks had pretty weak auto trannies. I just traded mine in this summer for a car
because the trans was about to give up the ghost. My former boss has one that the trans grenaded with under 85k on the truck. His buddy went through 2 in his 7.3. So my point is, unless you know for certain the trans has been rebuilt and to a greater standard than factory, add 4k for a properly built tranny. Of course there are some out there that last 300k miles, but the latter is definitely the exception, not the rule! This is just my opinion, though. Other than that, water pumps, and a couple of sensors, these are great trucks.
Hypothetically speaking, if that truck was completely stock, one old timer owner who left it stock and had every maintenance record for it, it would be worth $20k at most, IMO.
Are you dead set on a 7.3? If not, I would look into an 03-07 5.9 Cummins. I believe 04.5 was a desireable model year, for what reason I am not sure, but it sticks in my head from when I was looking for a diesel truck.
Good luck in your search.