All CC6500 where equiped with two gearing that can be switched from one to the other by the train driver when the locomotive is stopped. The original ratios were 100 / 220 km/h (although the sncf only used the CC 6500 at 200km/h max speed). Some where later modified with a 160 ratio instead of 220 to allow heavier train at 160 km/h. This system allowed to work with the DC 1.5kV alimentation limitation (mainly due to high current drain). I didn't find a satisfactory way to represent this in TF as using the real starting tractive effort value would cause the CC6500 to be way to slow with the way the game work. For exemple, a CC 6500 in low speed gear ratio would start at 210kN at wheel rim only, but be capable of 263kN at 74 km/h.
So, for gameplay purpose i decided that all the versions would start with 320kN (which is a bit less than the theoretical max tractive effort for the CC6500) and to differentiate the configurations with the max speed and maintenance price. The original CC6500 in high speed gear is capable of 200km/h for a maintenance price of 1.2M $/year (roughly the same as the Class 103.1), while the low speed version is capable of 100km/h only for 750k $/year.
The Fret livery is only available from 2000 when the SNCF separate its freight activity, and at this time some CC 6500 got their 220 gear ratio changed to a 160 gear ratio. The high speed version is capable of 160km/h for 850k$/year (a bit more than the Class 185) while the low speed version is capable of 100km/h for 650k$/year.
The SNCF only used this livery until 2007 but 7 years of availability being a bit short, i decided to remove the end year.