I have never seen an external oil cooler for any Kaiser Frazer hydramatic transmission. I don't know if there is a lube pressure port on the hydramatic transmission case, but I never looked. If the is a lube pressure port on the case you could install an external cooler. A lube pressure port would have about 10 to 15 psi coming out of the transmission. You would only need a return port into the case that would open into the case above the oil pan. The early hydramatic and automatic transmissions used air flow over the torque convertor by the shape of the lower cover to direct air flow into the bellhousing area. Early AMC used a baffle on the torque convertor to cool the fluid. If my memory is correct there is an opening in the hydramatic torque convertor lower cover. When these cars were made folks usually didn't drive 25 miles stop and go to work. Trips were short, heat is generated in an automatic mainly from torque convertor slippage. Kaiser Frazer hydramatics also used a dual stage torque convertor. Heat was generally not a major problem in early hydramatics, so an external cooler is not really needed unless pulling a trailer up hills, and that type of use.