RMS in a 68 Barracuda, oil pan problems

the trans cooler is 52 passes old now.... and when I was in Sacramento going rounds we did start to have issues keeping the trans temp manageable. Our next thought is to attach it with quick release pins and simply drop it into a pan of water and let it run in N for a bit to try and get the temp down..... think the last pass I went to the line with it at 220 which isn't real bad, but was higher than the previous passes by 40 degrees or so. In the name of consistency I'd like to have it lower.