If your delta is with in specs, there is no need to change the oil cooler. When they speak of flushing the coolant and switching to a ELC CAT EC-1 rated, then your gonna need to use Restore cleaner. The Ford Gold coolant has silicate in it, the ELC CAT EC-1 coolant is silicate free and won't mix well with the silicate residue left in the system from the Ford Gold. The Restore coolant cleaner is a chemical that removes the leftover silicate from the Ford Gold.
3rd paragraph down explains this also.
Things to consider about owning a 6.0L