Finally changed the oil, I had added a qt of atf to the oil shortly after I got it running and felt 500 miles was plenty of cleaning. Probably should have changed it sooner, the drain plug had a little more gunk on it then I’d like, and the filter actually had some sludge caught under the filter element. I didn’t find any large pieces of anything, and no real glitter which is good. I’ll run this oil for 1k and change again, with a full synthetic and better longer lasting filter. Probably Fram gold, since they are an all metal construction inside. It’s likely this truck will get less than 5k miles a year so a yearly oil change interval should be fine for it.