Peter - are you running a higher stall convertor than standard? If so, these significantly increase the trans fluid temps. The guy that built the Powerglides for both my cars basically says that you can't go wrong with the biggest trans cooler possible. Greater volume, cooler temps, happier trans. My trans temps are generally around 190F, with engine
oil around 200F. You might find your engine runs a few degrees cooler without having the trans fluid routed through the radiator.
Is your car back together yet?