Thank ou Linda. Appreciate your help very much. The previous owner said the original head gaskets were never replaced on this RV.
FYI: Brian McCamish (https://www.brian894x4.com/V6headgasketrecall.html, https://www.brian894x4.com/index.html) of Portland Oregon, appears to have a lot of experience with 1990'sToyotas. In his above web page, he advises that "Problems with the V-6 head gaskets always seemed to fail early in the engine's service life for no good reason". I hope this is true.
Thanks again.