Bob,
I know nothing, but I checked out the 59/60 Chevrolet trucks because I have 261 engines from 1959 and 1960 Chevrolet trucks (6000 series, I thought).
It looks like 1958 was the first year for the use of the three truck names Apache (light duty), Viking (medium-duty), and Spartan (heavy-duty).
It looks like the 1959 Viking 60 series (6000 series?) had a 261 as the standard engine.
Maybe Task Force owners will add useful information and corrections?
The Shop Manual would be for all trucks.
Here is a 1959 Chevrolet Truck Specification Manual - this is a 3.5MB download. 
