[Dan Case]

Original belts are narrow ones. They were tough as I know of original cars still using them five decades later.

Tossing belts is usually an indication that one of the engine sheaves is the wrong one. The CSX2201 and later Cobra system was designed around 1963 Ford 260/289 sheaves for crankshaft and water pump applications. 1963-64 engines use the same parts. Starting roughly August 1964 the new “1965 model” engines got new sheaves with different groove locations relative to the mounting hubs. See Bob Mannel’s book.

Mixing 1965 sheaves with a CSX2201 alternator system will most likely lead to fan belt issues. When I bought my red car somebody had installed 1965 and later water pump sheave. The alignment with the original alternator and crankshaft sheave were quite visibly off and the belt had to be super tight to keep it from walking off the incorrect sheave. Super tight fan belts are not a good idea. The purchase of a good used 1963-64 water pump sheave solved that problem.