The stuff in my coolant isn't any type of soluble oil that I've ever seen. It beads and floats and looks just like motor oil. I think a little more aggressive pressurized flush of the coolant system may be the next step.
Thanks for all the input. I can see that stovebolt is going to be a valuable resource for us while we (we being my 16 year old daughter and I) play with this. The down side to this little father daughter project is that she already has designs on the beast. My office is 1.8 miles away and this truck was intended to be my every day driver but I'm betting I'll be driving her Volvo as much as she does.
