I checked all of them with an ohm meter going from the small terminals positive to negative, I wire wheeled the tops of all terminals. Readings are all pretty much bang on 2.0 ohms, some are a bit less as low as 1.7, some are as high as 2.2.
Then i checked some of my "other" coils(not the aluminum ones). they are all pretty much the same, couple aftermarkets were as high as 3.2, but most are around 2.0-2.2
here are the pics of the GM aluminum ones, and some of the numbers