I just put one in my 1982 Westy with great success.  Hop on Ebay and buy a used RX7 oil cooler the big oil to air ones are about 22 inches long, 2 inches thick and 7 inches high.  They have a built in thermostat that opens at 180 degrees.  I mounted mine above the transmission, I had to weld some brackets up there to hold it, I plumbed in a remote filter and just pulled the oil from the stock filter location.  There is not much air flow up above the tranny, so I mounted four  4 3/8 inch fans to the back side of the cooler.  On our trip to the Outer Banks this summer oil temps never got above 180 NEVER.  You can drive what ever speed your cylinder head temps will allow.  By the way the tray that comes with the fans and mounts them all as a unit is great, just cut about an inch out the middle of it, weld it back together and it fits right on the RX7 cooler like it was ment to be there.   
below is a link to the fans I put on the cooler.

http://www.surpluscenter.com/item.asp?UID=2003062716383426&item=16-1235&catname=electric

Date:    Tue, 4 Nov 2003 12:15:59 -0500
From:    Tom Hewitt <thewitt60@HOTMAIL.COM>
Subject: External Oil Cooler

Have completed a re-build on my 82 Westy, Air Cooled motor. Would like =
to use an external oil cooler
on this motor. Do List members have experience with placing a cooler on =
the 2 liter Air Cooled engine?
What is the best method to connect the oil lines to the motor? Where =
should the output/input be connected. Would braided line be best. Whats =
the best location for the cooler? =20
Would appreciate some List experience on this one.   Thanks

Tom Hewitt

82 Westy
67 Bug

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