Fluidyne DB-30618 Oil Cooler. Was on my race car for two seasons and did an incredible job keeping oil temps down. Oil temps never went above 210 using this cooler, even when ambient temps reached 95 degrees. I did spin a rod bearing with this oil cooler so you will want to have it cleaned by someone like Pacific or your preferred cleaner. I had them clean my 914-6 oil tank for $125 last fall and they did a fantastic job.
You'll find specs for the cooler here.
Cost over $400 new. Buy for $100 plus shipping.
Click to view attachment
Click to view attachment
Click to view attachment