Try this - a presentation from the late Richard Hendrickson. It concentrates on the pre-1960 era. https://docs.google.com/file/d/0Bz_ctrHrDz4wcjJWcENpaDJYbUU/edit
Shock Control
But I would also like to know when 80- and 100-ton trucks came into use.
Trucks with 70- 77- and 100-ton nominal rating came into widespread use by the 1960s.
Also, three-spring trucks as oppoesed to two-srping.
That varies by design. Trucks with 100-ton capacity almost all have three outboard springs. Others vary. I'll use some examples from different manufacturers.

This Tangent 50-ton truck has two outboard springs.

This 70-ton American Steel Foundries (ASF) pattern 70-ton solid bearing truck has two outboard springs and three in the row behind them.

A 70-ton Barber pattern solid bearing truck with three visible springs.

A 70-ton Barber roller bearing truck with two outboard springs, and a different arrangement of the sideframe casting under the bolster compared to ASF.

A different variety of Barber pattern 77-ton sideframe with three visible springs, similar to their 70-ton sold bearing design.

Note the 70-ton ASF pattern roller bearing truck has a similar spring arrangement to the 70-ton ASF version with solid bearings.

The National type C-1 70-ton truck had a distinctive triangular spring arrangement.

A 100-ton Barber pattern truck. The sideframe cross sections are heavier than the lower capacity versions, and the wheelbase is longer (typically 5'10" if I'm remembering this right vs. 5'8").

This ExactRail 100-ton ASF truck has a different sideframe design compared to the Barber pattern.
Note there are plenty of other variations, including 125-ton trucks, low-profile for specialized cars like autoracks, and so on. Multiple casting companies manufactured trucks with the above patterns, and there could be differences between separate plants for the same manufacturer (e.g. the Moloco ASF 70-ton truck represents one specific to the Granite City, IL plant) Sometimes good prototype information comes with the product descriptions on sites like Moloco or Tangent.