Terry,
If your document lists OEP220, then it is not an original document. The OEP220 (EP90) was substituted for SAE140 in postwar years to make it more compatible with other vehicles, but because of the poor sealing arrangement in Tracta housings, the EP90 is more prone to leaking than a Straight 140 oil, especially in your warmer climate.
A point worth noting is that the tracta spherical challis has bronze bushings for the shaft and EP oils can effect these. The bushes are prone to wear and it is their fit that stops oil from migrating from bevel box to outer tracta and hub. Very often you will find on checking levels that the outer has too much oil in it.
cheers Richard