Topic: 78' 550k rear shock question

[Reedy26]

I'm looking to go with a Ohlins reservoir type rear shock setup on my cafe build.

My bike didn't come with any rear shocks, so question 1 is what is the distance between the mounting points on the shock?
 
Question 2 is what kind of spring rates were used from the factory?

I'm probably going to end up picking up a used set from another bike if it is something close that I can make work properly. 

[mrfish2]

The stock length should be 12.75 inches from eye to clevis. At least, that's how it is on my '76 550.