Your 731 VIN is definitely a 1960 VIN; the car was built on October 8, 1959 (give or take a day or two). 1959 Corvette production ended on August 10, 1959 (#9670), and 1960 Corvette production started on September 2, 1959.
BTW, Prince's reference on '54 VIN format is incorrect - all 54's had an "S", not an "F" in the VIN, and all 54's were built in St. Louis; only the 300 53's were built in Flint.
The "V" prefix on '55 VINs is there to signify that they had V-8 engines.