What board do you recommend for pull/dir for a T3D servo drive?

You might still use it, if there is firmware that puts the stepgens on the IDC26 connector and use a cheap BOB to wire in the drives. Requires also an DB25 to IDC26 cable, so all cheap stuff, but be warned that cheap BOB might limit the step frequency a lot.
You can just wire drives directly to IDC26, but that does require caution in proper wiring as those I/O pins are highly sensitive. Having said that, i use those pins on plasma machines and never ever had any die.
But if you still want to get a new board, get the 7i96S as it can be found easily and can be expanded easily by adding, say a 7i84 for 32 more inputs and 16 more outputs, and say a 7i85 for more encoders and more boards like 7i84 or 7i70 or 7i71 or....

tommylight wrote:

You can just wire drives directly to IDC26, but that does require caution in proper wiring as those I/O pins are highly sensitive.

This means no BOB.