Hey man, looking to do the almost same thing. The oilpans on the 6.9's are reversible, so you can have a couple different configurations for clearance there, and the swap would be much easier into a lifted 4x4. A guy that I know has put a 7.3 into a square body chevy says it is a tight fit but will work.
The reliability of the NA 6.9l IH diesels have been unmatched by any other diesel motor I can find, except for maybe the Cummins, but I don't have the deep pockets needed for the Cummins. You can pick these motors up for next to nothing and usually the truck is falling apart around the motor, so they are a dime a dozen in perfect operating condition, well close to perfect. I see a lot more broke 6.2/6.5's in the junkyard and have yet to find one broke 6.9, which I think all the broke 6.2's and 6.5's is because people try to turbo the snot out of them, when that is not what they were designed for.
Think you would be better off going to a zf5 or something like that, but if you have the access to a machine shop, the sky is the limit with what mods you can do.
