Is your 386 a Automatic or Standard. The 386 im looking at is with a ISX and Automatic. But the truck has 623,000 miles on motor and transmission. I heard the cummins let go between 600,000 to 700,000 miles.
Mine is standard...18sp. It just turned 800k with no signs of needing anything...knock on wood. Has had one turbo about 675k. Premature cam failure can be an issue but that is mostly due to too long of oil change intervals.