The heavy duty Torque Conduit has the same recipe as
the medium duty Torque Conduit.

The heavy duty Torque Distributor has the same recipe as
the medium duty Torque Distributor.

(no idea how to add the "balance" tag to this yet, sorry)

Further to this issue: I just made 3 medium/heavy duty Torque Conduits (Iron Torque Shaft and Gear Sets) but once I placed them in the world, they became Light Torque Conduits.