Sorry – I should have posted this on the Forum site rather then the Activity Stream page
First step is to download from this site the instructions for Accessory Kit 132 (AK-132). This was the factory provided (and approved) kit to install an oil cooler on the AA-1 through AA-1B. This uses the parts found on the AA-1C. Ken Blackman was making some of the components from this kit, Roscoe will know more about that.
Another option is STC SA2169NM from Maynard Crosby that calls for the installation of the oil cooler, along with a Sensenich prop (same as on the AA-1C, but might be lower pitch). This is a better prop.
It should not interfere with the Casper Oil Filter adapter.