After four massive years of sales success, the Mustang received its first major facelift. The new car grew in all directions and gained bulging flanks while losing the appealing sculpted flanks, and sales began to fall off a cliff. It was wasn’t all about the mid-life changes that blunted the Mustang’s appeal, but it was just as much down to changing times. The ultimates were the Mach 1 and Boss, which Ford produced to fight the Shelby cars in the showrooms. These cars had up to 375bhp and could sprint to 60mph in under six seconds – are are valued accordingly.