What you may be seeing is corrosion. If it is white/gray colored and looks like rust pattern, it's corrosion. This is when I say stop using Morgans and use some other brand of race fuel with a 10-14% oil content, not the bashing 18% oil content stuff. Those need more oil because it is a poor quality oil. And also, I recommend using after run oil if your truck sits for more than a day or two without being run. If you are gonna run it frequently, it shouldn't hurt. Those spots though sound like they are from the engine sitting for a week or more at a time without being run. You NEED after run oil to prevent that.

OH, and the only things that could possibly rust in the engine are the bearings and screws. The case, sleeve, everything else is some sort of brass/aluminum/chrome alloys which will not rust.