I have a 1964 and a half Mustang convertible VIN number starting with a 5F ending 8189

In 1964 production was in high gear for the newly designed 1965 Ford Mustang. The highly anticipated Ford Mustang was honored by being named the Indianapolis pace car of 1964 and Ford stepped it up to accommodate the rising status of their new design. A special convertible version was adapted as the pacer. It was manufactured in white with a blue stripe on the hood and trunk. Ford also made 230 extra pace cars, available in convertible and hard top. The 64 1/2 convertibles had a 289cid engine, and the hardtops came with the less powerful 260 V-8. Thirty five convertibles were sold to dealerships and 195 hardtops were given out in dealer contests held in April of 1964. Clearly the new Ford Mustang was suddenly everywhere! It was even featured in 1964’s Bond movie, Goldfinger! Yes, the Mustang was an instant hit! A true royal gem in Ford’s car making history. It was the most successful release Ford had made since the 1928 introduction of the Model A and it has stood the test of time. Ford is still continuing the Mustang line and even the newer Mustangs are a modern collectors item. Although originally the Mustang was advertised as an early 1965 model, Ford made some changes to the later 1965 models that differentiated the two, and it is known today as the 1964 1/2 Mustang (1964.5 Mustang). Thus, the term 1964 1/2 or 1964.5 was eventually coined. What were some of the differences between the 1964 1/2 and 1965 Mustang versions.The first Mustang rolled off the assembly line March 9, 1964, and it made its national debut on April 17. With a list price of $2,368, by the weekend, 22,000 cars were ordered and some 303,408 were built that first year. Through 1966, Ford sold more than 1.4 million of them. There were up to 70 options available. Initially offered only in hardtop and convertible models, a new model was introduced in September 1964, the Fastback 2 + 2, which debuted as one of the three 1965 models. Model year 1965 took off just like 1964 1/2 did with more than 550,000 sold. So, why change a good thing? The 1966 model was basically a carryover and on March 2, 1966, less than 24 months after its introduction, the one-millionth Mustang was built. Certainly Ford made up for the Edsel fiasco. In 1964, the standard engine was the 170-cu.in. straight-six with 101hp and had a 8.7:1 compression ratio. There were three optional V-8s beginning with the 164hp/260-cu.in. engine and a 210hp/289-cu.in. V-8. The top performer was the 271hp/289- cu.in. V-8. This engine featured 10.5 compression, four-barrel carb with manual choke, solid lifters and dual exhaust. The original Mustang came standard with a three-speed manual floor-mounted transmission. An optional 4-speed was available, as was a Cruise-O-Matic automatic, except with the 271hp V-8.

ANYWAY= That said, Mustangs produced between March 9th and July 31st of 1964 are often coined the 1964 ½ Ford Mustang

Look at the tag on the drivers door. In the date area 27G would be the 27th of July 27H August and so on. Unless I have been misled. Hope this helped