Encoder counts for Spindle

Hi
I am finally getting back to work on my old HAAS VF1 , ordered one new motor and controller
so If I can get the Z axis and tool changer working together then I will get the other two for the X and Y

I am going to try to orient the spindle electrically , it used to use a detent pin to lock in orient position.
And rigid tap if I ever use it.

So I have to add a spindle encoder and would like to know
what the recommended Counts Per Revolution should be.

Is 400 not enough? Is 1000 more than enough?

I am using a 5i25 and 7i77 , and I figure max rpm of the spindle is 6000 rpm
so I dont want to over count ...

Thank You for any advice.
Tim

Rigid tapping is more critical than threading but anything from
100 line (400 counts) to 1024 line (4096 counts) should be fine