Hey Mike,
you can run any VFD/spindle that is rated for 110 V at 100 V. At Hitachi, these models are known as “100 V class” because they are for countries with voltages of 100–120 V, they have the “200 V class” that are for countries with voltages of 200–240 V and there is the “400 V class” which means they are for countries with voltages of 380–480 V. For example, the 100 V model says explicitly “100V –10% to 120V +10%, 50/60Hz±5%”. The same applies to other manufacturers. A VFD does by itself not produce the voltage. It takes the AC voltage at its input, rectifies it (transforms it into DC), stores it in capacitors, and by using six IGBTs, it forms a three-phase current. The frequency at its input is irrelevant since it is transformed into DC anyway. And at the output, it produces the frequency itself, which is usually 100–400 Hz for driving 6,000–24,000 rpm spindles. But it just uses the voltage you give to it at its input. And a spindle, which is an induction motor, can be driven with any voltage. You can drive a 220 V spindle at 380 V and vice-versa. What matters is the current, and the currrent is always set and controlled by the VFD.
However I would avoid to buy a 65 mm spindle because of this known disadvantage. With the additional 80 mm mount, the spindle clears the stepper cage.