Phil Ramsey, "Oil Filter Advice", Machinery Lubrication Magazine, November 2004.
http://www.machinerylubrication.com/art ... icleid=681
« The VW Super Beetle had a full-flow filter after 1972 until production stopped in 1980. There was also a full-flow filter on the 1975 VW sedan and the 1980 VW convertible. »
Although some of my VW books, mention the changes in technical specification from one production year to the next, there is no mention of any full-flow oil filtration being introduced, on any VW Type 1 style engines.
Jerry Sloniger, "The VW Story", Patrick Stephens Ltd., 1980, ISBN 0-85059-441-3
Clive Prew, "VW Beetle", Grange Books, 1990, ISBN 1-85627-034-3
I would certainly have expected to see such a thing mentioned, in the following book:
Tom Wilson, "How to Rebuild Your Volkswagen Air-Cooled Engine", HP Books, 1987, ISBN 0-89586-225-5.
I vaguely recall the VW Type 1 Beetle 1302S, being equipped with the 50 DIN horsepower, 1584 cm³ displacement, AS-Series air-cooled engine, which was also employed in the 1974~79 VW 1600 Type 2. One VW Type 1 & 2 enthusiast of my aquaintance, who has a 1978 VW 1600 Type 2, certainly has not mentioned any factory-fitted, full-flow oil filter.
VW Boxer Engine Codes by Brian Verbeek
http://www.type2.com/library/identifi/boxeng2.htm
Bay Tech Clinic > Engine & Transmission > Engine Codes
http://forums.kombiclub.com/showthread.php?t=7284
To the best of my knowledge, the only VW Type 1 style engines, which were factory-fitted with any form of full-flow oil filter, were those of the late-model (i.e. circa 1990s), Mexican built VW Beetles, with Bosch Digifant fuel injection (not Bosch L-Jetronic, as used on North American specification, 1975~83 air-cooled VWs), catalytic converter and hydraulic, self-adjusting cam-followers, which required properly filtered oil, for which provision was made, using a filter pump (i.e. oil-pump housing, with integral, cast-in, horizontal oil-filter mounting).
There certainly was a development of the air-cooled VW Type 1 Beetle style engine, which had a full-flow oil-filter mount, which was cast as an integral part, of the left-hand half of the engine crankcase, in a similar fashion, to that of the 1983~92 VW 19/2100 Type 25 (i.e. Vanagon or Transporter T3), water-cooled, spark-ignition (i.e. gasoline-fuelled) flat-four engines. These air-cooled engines (with CT or CZ engine-number prefix), cooled by a crankshaft mounted fan, similar to the VW Type 3 & 4 style, air-cooled engines, were used in the non-North-American specification, 1980~83 VW 1600 Type 25 (i.e. Vanagon or Transporter T3), as discussed at the following Internet links:
http://www.tunacan.net/t4/tech/ct-cz.shtml
http://www.type2.com/library/engineg/boxeng.htm
I also know of one example, where a complete engine assembly of this type, including coverplates and all ancillary components, was substituted into a 1972~79 VW Type 2.
And go like a Boeing too 
