That’s an interesting piece of data. And good to know. Is it US spec and are you mostly certain it came from the factory that way? My 3/79 does have the original cooler. Only 5 months apart off the line from yours. What’s also interesting is that Toyota assembly builds cars and trucks for different regions all at the same time, not in batches. IOW, an assembly worker might assemble one truck for the US market with all the emissions and such, next truck might be for the KSA, next one is JDM right hand drive, and so on. So they continued to build with AND without oil coolers side by side well into the ‘80s. You can tour the factory today and watch this happen with new vehicles.My ‘10/78 Federal spec does no have one, no issues here and I am in Arizona FWIW.