The 2005 coil springs, integrated brake controller, upgraded transmission, tighter turning radius, a more modern looking front grille, etc, won't matter one bit when you're stuck on the side of the road with a catastrophic five figure, cab off, three week repair to have to finance.
The cost of having to pay for two tows at once to pull you off of the side of the road... one for your truck, and another for your trailer, plus the nights at the local motel and the rental car, will likely far exceed the cost difference between the two trucks you are considering.
I take it back... the tighter turning radius might come in handy for the tow truck driver to steer your disabled truck in line with his flatbed.
If you are just now trading up from a 95, it doesn't sound like you are looking to waste an extra gallon of fuel to be the first guy to the top of the mountain pass. So unless you have an extra $8,000 to $15,000 in cash handy to cover the well known, well documented repairs needed to either fix or "bullet proof" a motor whose history you have no idea about, I'd take a pass on the 2005.
The 7.3L may be bit slower (although I've seen highly modified 7.3L's pull 11 something second 1/4 miles at the track), a bit older, and turn around in a bigger circle, but at least it manages to do so on it's own power. There was an article two years ago about an RV delivery guy reporting over 1.2 million documented miles on his 7.3L. And many more mileage reports exceeding half a million miles and still running strong.
The 6.7L from Ford looks promising. But that remains to be seen long term, and remains an order of magnitude more expensive to get into.