Received my latest Vans supplies today, including the mount for a remote (firewall) mounted oil cooler. This was the version that is designed for extremely hot environments. I'd have to say that Arizona is typically one of the most extreme hot zones in the country. So I might be pessimistic but I'm going to the 'big cooler' side of the design. Plan to use the oil cooler that was mounted for the engine in the helo (R22) configuration as an O-360-J2A. It's slightly larger than the O-540 version that Vans sells.
If it's TOO big, there are baffles, vents, and also can still be replaced with the next size down, but I have this one and the price is right, too.
The adapter of .063 3/4 x/ 3/4 angle is very straight forward and adds (of course) 3/4" to the space needed. The oversize cooler is also going to be a little bit of a space hog. Position is an estimate and will probably have to be determined after a lot of F/W components have been secured.