Hi all,
Ya, the air cooled engines already have a oil cooler but over the years crud
can get packed into the imput side thus reducing the exchange of heat.  All
the dirt, oil, cat hair and chicken feathers that get sucked into the engine
compartment get blown down past the piston cylinders and oil cooler. If I had
a high mileaged engine I would remove enough sheet metal to check how clean
the oil cooler /radiator really is.  It is a real PITA but worth checking.
It may even be worth replacing the two high temperture seals that go between
the cooler and the block while you are there.  The cooler is easy to remove
after you get the blower cage and sheet in removed.  Have some degreaser like
"oil eater" (works great but never use on hot aluminun) ready so you can
clean things up as you go along.  A clean engine is a happy engine ;-)  My
brother once bought a nice type 3 and then promply burned up the engine
because the oil cooler was plug by oily crud.
Cheers,
Kevin Dawson