David,

I've described my installation of an 11" x 11" oil cooler behind the right
rear tail light, complete with external oil filter and thermostat with my
2.5L Subaru conversion in my '86 Westy.  This works great keeping oil temps
between 185� and 210� under all conditions, instead of 265� during summer
interstate driving.

My write up is complete with pictures and item part numbers.

This description can be found in the SubaruVanagon Yahoo list Files section
in the Oil Cooler folder.  See Oil cooler - 11x11x1.5 diagonal written by
dontemail2002.

https://groups.yahoo.com/neo/groups/subaruvanagon/files/Oil%20Coolers/

I used Aeroquip Socketless hoses but I would recommend something else
because these have formed small cracks in the hoses around the barbed
fittings after maybe 6 years.

I know there would be some interference with other engine installations but
I am mentioning it as an example of another working oil cooler installation.

Ed