Looking at 2 1999 T600's, which one would you choose?

Looking at 2 1999 T600's.
First one has a 12.7 and 10 speed Owner tells the same old story. Guy he bought it from told him it was rebuilt 2 years ago. But he lost the paper work. Now would he not need to keep the paper work in his records? Where if he was to get called in for a audit. He has proof that he did get that done?
Roof and side faring under the cab, not under the sleeper.

Second one has a N14 1,008,000 miles overhauled by owner that has owned the truck from 2005 until now. Has paper work on the rebuild. Dyno at 400 HP to the ground. This truck has 3.70 gears.
Also both have 24.5 tall rubber. Second one has full faring, will be taking the sleeper one off if I buy it.

Being there both the same year truck. But different engines. Would the N14 get close to the same MPG as the Detroit? Also first truck has the Diamond tuck interior. Where truck #2 has the straight line stuff. So no tilt steering wheel. Not sure what else it does not have over #1.
Both are single bunk trucks also.
Price is the same on both trucks. AC is not working on #1 at this time. Figure it the blower motor resistor.

Wondering if one truck is better then the other?
Pete

 

The N14 was a O/O truck. He had the engine rebuilt and has all the paper work with it. But agree have no ideal if it was done right.
Bought a 1995 T600. Got home with it today. Thinking with a little work its going to be a good one. Ran it 75 in Tx and 70 to 75 across I-30 in AR. And this am before daylight around 75 on I-40 to memphis.
Pete