"gear oil is too runny and often leaks"
Showkey,
At about the time I started restoring my '36 Chevy pickup I bought a new 1971 Dodge van (that I still have). The factory shop manual for the van specified that gear oil is used in the manual steering box. That made it clear to me that gear lube is an acceptable lube. 46+ years and 360,000+ miles later the van is doing well with gear oil in the steering box.
If I had the truck restoration to do over I would use Corn Head grease or an equivalent because it would save the time I spent looking for a narrow sector housing seal and machining the sector housing for the seal. But I didn't know about Corn Head grease then and the gear oil solution has worked out fine.
One advantage of the oil is that it's easy to tell when the box is full so over/under filling is not a problem.
