I believe they are the incandescent type and use a 11µa quadrature sinewave output, so unless you convert to RS420 differential, they may not be suitable for Dynomotion?
You will however be able to get rid of the 6.5v/1krpm DC tach's, I just remove the brushes to avoid any problems in the future.
As you can see by the encoder disc, they are pretty coarse resolution, but they make up for it in the sine mode by using the arctangent function to increase the res.
It may be better to source some through shaft TTL encoders?
I usually run the A-M-C drives in the torque mode and AMC have an app note on setting the pots for this mode also.