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Based on the message count that you have and the question about what fluid goes here - I am thinking you are new to the hobby and this group. So,
Welcome to the Outfit! Snap us some pictures of the rest of your truck. That way we can see what you have going on. You may want to spend a few bucks on some new rubber under the hood. Radiator hoses and V-Belts so you don't get disappointed when you get a few miles away from home. If you can gather some pictures taken and posted we can rename this thread...
Anyhow, echoing
@GopherHill 's suggestion about the Technical Manuals (TM's) and
@Elk1111 's pointer to the power steering tank... You are off and running. Get us some pictures to help the
Picture Hounds around here!
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