65 Dart Wagon Conversion to a Sedan Delivery

I agree with you and disagree with the "transmission expert" on how to mount the cooler. Like engines, automatic transmissions have an operating temperature range. If you run to the external cooler first, you could cool the fluid below normal operating temperature. When the fluid goes to the radiator, it would be heated back up. Fluid back to the trans is at operating temperature. If you do it the way the 'expert' recommends, your transmission could spend most of its time below normal operating temperature, with possible reliability issues.