Bummer Karen if I remember right you put that motor in a short time ago. I capped of my existing cooler and used a 70273 cooler as Jim suggests. I mounted mine in front of the a/c condenser and secured it to the cross frame directly under it and braced the top to the bottom of the blower housing.it is about 4 or so inches in front of the a/c coil. I picked up a small electric radiator fan at the wrecking yard to blow more air thru it. I ran 5/8" copper refrigerant tubing a short distance with copper elbows terminating with 1/2" female pipe fittings and connected it to JR's stainless lines with 1 line shortened and straight fittings replacing both 90 degree fittings. I doubled up the spring in the filter bypass to raise the relief pressure from 5 psi to 10 psi. When you rebuild your heads don't let the shop put solid bronze guides in the exhausts or they will seize the valve stems on a long mountain grade you don't want the nightmare I reciently experienced . My cooler and associated piping required an extra 1 1/2 to 2 quarts of oil on initial fill up.

Rob what I meant was the oil cooler pulls heat out of the engine via the oil but then that hot air flows into over the radiator, some of which reenters the system via raised coolant temps durring max system loads. But the same thing happens with the in tank setup. I would think in very cold weather once the stat is partly open, the oil would not be cooled as much as the air stream cooler. Whereas going down the road in cold weather you could overcool the oil, over reducing piston temps, loosing some MPG.
Interested to see the test results on the bypass valve(s). I was looking at the cooler addaptor for a Turbo Regal and it's a smaller version of our same unit for a PF47. There is another bypass valve in the cooler adaptor. Interested to know the total count and when they open and the effects of heavier 15w/50 oils some lean towards especially at cold startup.

200 is way too cold and not above boiling point of condensate water. Remember, each gallon of fuel you burn produces over 1 gal of water combining hydrocarbons with H and O2 from the air. Also oil splash cools pistons. Cool pistons absorb more heat energy that .could otherwise be used to push them down and do work. Loss of some MPG.