The large EV3 motor has a different form factor then the NXT motor. I had to redesign the legs of Agilis to make use of these new motors.
The new design is smaller and much prettier to the eye. The smaller size and all the triangular shapes makes the leg very stable. The new leg can be fitted on the same triangular frame that was used for Agilis.
Here are the building instructions for the new leg.
If you only have two large EV3 motors you can easily modify the leg to use the EV3 medium motor. This motor can be attached directly to the drive axis of the wheel and to the underside of the frame. You will have no gearing. But as the medium motor rotates a bit faster you will still have plenty of speed in your robot.