A couple of days ago I posted the following question. Can anybody help?

Looking through the archives for diesel topics I came upon a reply by Martin Jagersand (week 2 July 99 "82Diesel cooling problem") to a overheating problem on a diesel vanagon. As Martin has a very nice diesel only website my eyes perked up for the "real scoop". He stated in his reply that he had inspected 3 diesel engines whose demise was related to overheating caused by the wrong waterpump. Wrong being the more common Rabbitt/Jetta type vs. the correct Vanagon pump. The difference between the two is in the hub and pulley not in the impeller. Question: My 79 Rabbitt diesel has the alternator-pivot tensioning method and works fine even though it has "shallow angle contact" on the waterpump pulley. The Vanagon has a awkward but larger angle contact 2 belt pulley system which is harder to adjust. Scott Foss Turbo Diesels offered a single belt conversion for Vanagons using a different pump (Rabbitt/Jetta?), waterpump pulley, crankshaft pulley, and one single belt. What am I missing here? By looking at the stock Vanagon set-up I could use one long belt and tension it at the alternator pivot but maybe the belt doesn't contact the pulleys properly? Why not just copy the Rabbitt/Jetta layout?