The Datsun 1200 Steering Gearbox uses GL-4 80W-90 or 85W-140 multiweight, same as the Transmission lube.
Nissan recommendation * API GL-4 * MIL-L-2105
Such as: * Chevron Multiservice Gear Lub. 75,80,90,140 * Esso Gear Oil GP 80,90,140 * Mobil Mobilube EP or GX 80-90,90,140 * Shell Spirax 75EP,80EP,90EP,140EP * Sunoco Multipurpose Gear Lub. GL-4 80,90,140 * Texaco Universal Gear Lub. EP 80,90,140
1972 USA Owners manual (Page 23 ... ):
Recommended Lubricants