what oil do you guys use for your manual steering box?

'65 Chevy service manual says use chassis lube i.e. grease.

A good lithium based chassis grease is fine. Just don't completely fill your manual gear. When underhood temperatures rise, the grease needs some air volume inside the gear for it to expand.

If you completely fill the gear, it is possible for the pressures inside the gear to increase to a point where the input shaft and/or the pitman shaft seals can blow out.

alright - thanks alot! time to pick up some chassis grease

to properly fill the box, remove the center bolt that is on the pitman cover and the upper most bolt. Fill at the uppermost bolt hole until the grease comes out of the center hole, install both bolts and torque to spec..