I got a full gasket set from the machine shop and I am finishing up assembling the motor. Besides the o-rings for the injectors, I have 5 O-rings. Of these, there are two matching pairs, both of which appear to be the correct diameter for the drive. Here are some measurements I took of each of these pairs of o-rings.

Set 1:
Outside diameter: 1/2"
Thickness of O-ring: 3/32"

Set 2:
Outside diameter: 1/2"
Thickness of O-ring: 1/16"

Which of these are the correct o-rings for the water pump drive?

Also, what is the bolt hole on the driver's side of the engine block, just forward and above the rear freeze plug? I don't think it is a sensor and it's been a few months since I pulled the motor.