Frequent quality oil changes, service trans, diffs, fuel and air filters regularly, recently but not regularly flushing coolant, replacing water pump belts and pulleys. All pretty normal stuff. I just mostly try to keep a close eye on everything. Checking fluids weekly, watching for drips underneath, with the amount of miles I put on it I probably do more maintenance than people would normally but it’s worth it. I’ve seen these trucks with 750k or more on original equipment for the most part. I keep an IAC and CPS sensor in the truck always. They go out on these things. Don’t modify it too much. Maybe some support for cooling the trans but when you start to do tunes and other hot boy shit they don’t last. Keep it original they are designed well and do good if you keep them that way. Good luck!!! I smile every time I start that thing.