Nobody built cars to disappear quite like Chevrolet built the 1964 Biscayne, the cheapest full-size car in the lineup, yet a rare handful of buyers spec’d it with the same 409 big-block that made the Impala SS famous. Stripped of chrome and drag-strip focused, a 409 Biscayne is arguably the ultimate factory sleeper of its era. Here is why even dedicated Chevrolet historians cannot agree on exactly how many were built.