1985 f250 IH 6.9 4X4
 

I've been talking with a guy about purchasing his 1985 f250 with a 6.9idi mated to a 4 speed standard 4 wheel drive and have a question. The truck in question about 160,000 miles on it and i'd say at least half of that was used to pull a fifth wheel horse trailer. is this truck going to develope transmission issues anytime soon or are they pretty stout? Could other issues arise from this. The current owner says it doesn't fall out of gear under load.

The plan for the truck is a 2'' lift, 35'' tires, detroit locker for the rear and thats pretty much it. I want to build a reliable truck to drive on road trips this summer out in the back country of California and not worry about being stranded 70 miles from the nearest help. Thanks for any input you all may have.