Detroit Diesel 12.7

was wondering if anyone had some knowledge about this engine. I'm looking to buy a 01 Intl 9400, has the detroit 12.7 engine. I went and looked it over and drove it. I have been driving a 98 FL century with the same engine the last few months btw that has a fresh rebuild. When I went to see this Intl 9400, it seems to run quieter and nicer than the 12.7 I been driving, the current owner said it has around 600k on a rebuild with new bullgear installed recently. The only concern is, the ac is not working due to the accessory drive being removed. He says its currently getting 8.5-9.2 MPG. Seems to shift nice, runs nice. Needs minor things like a couple tires. Little over 1 mil on the odometer. I'm getting it for under 7 grand. I'm just trying to see if someone would remove the accessory drive gear to improve fuel econ or would that be something that the last bullgear destroyed on its way out? I'm cool with no ac since i drive at night almost always but I'm also not looking to get screwed either. As for the AC, I'm thinkin I might just get a roofmount ac installed or something that would get some cool air flowing, its a small sleeper that i most likely will not use ever.

 

Thats why i'm skeptical about it, just not wanting a major repair bill coming too soon. He's explained his reasons for selling such as the small sleeper, he's a big dude who stays out OTR and he got a deal on the truck he wanted so this ones sitting now.

 

The truck actually has 1.2 mil on the odo, im told the engine is at about 650k, bullgears just installed very recent.

 

he says he had it removed at the time the bullgears got replaced, planned to have a roof mount ac installed. He says this is why the fuel econ is so good. I'm hoping nothing is messed up, I can live without the ac being that I mostly drive at night and live in Michigan, local runs only. I drove it and had him drive it also and seems to be running better than most the trucks im used to driving. I need the thing to get me thru the next year or so without having to mess with any big repairs.