Then the torque rod system is ever better. The rod in the other wing which is driven by the same servo operates the pusher throttles (the same way the two ailerons operate in opposite directions). You just have to use two throttle servos each with their own pairs of opposite moving torque rods. I've seen much more complicated setups with tri-gear mechanical retracts.

One servo operates the tractors in one wing and the pushers in the other wing. The second servo does the opposite.

Since the engines are back-to-back their throttle arms are on opposite sides and the pushrods from the torque rods won't get in the way of each other; they're staggered down the wing.