Run a C-Wire to #2 on a Taco Valve? Other location?

Sorry...I'm a newbie on this forum. I've searched, and searched, and have found multiple answers (and maybe they are all accurate).

I have a Weil-Mclain Gold CGa Boiler with two Taco Zone Valves (one thermostat per).

I like many others, want to get into the Smart Thermostat world. I'm specifically looking to install an Ecobee 3 thermostat - starting with one, and adding another in the future.

I only have a heating system. I live in Alaska - no need for AC or anything else. Hence, I have two wires going to the thermos. Red going to R. White going to W. Luckily for me, there's a spare Green wire on both ends that I want to use for the common.

I've read the following:

1. Connect a common wire to #2 on the taco valve that goes to your corresponding thermostat.
2. Connect a common wire to the C at the transformer inside the boiler.

This may make me sound more of a "newb" but using a multimeter, I can get a constant 24v when using one lead on #2 of a valve and grounding the other lead - regardless of when calling for heat. This would make me think that this would be a good location for a constant - however, I can get the same when doing the same thing on the #1 location on the valve.

A couple of poor photos:

First - how the wires go into the transformer. The WHITE wires from each thermostat go to a nut. From the nut a RED wire goes to the C on the transformer.

Boiler

The RED wires from the thermostats connect to #1 on the Taco Valves.

Taco Valve

I'm leaning towards the #2 on the Taco valves - but any assistance is most appreciated!