Leading timing 0 degrees.
Trailing timing 20 degrees.
So i expect the trailing pick-up to sit 20 degrees offset.

(picture stolen from internet)

But the two pick-ups are sitting 180 degrees opposite!

How does the trailing pick-up fire 20 degrees after leading, while it is sitting 180 degrees opposite to leading?

 

You will find that if you rotate your engine cw bring it so the dist. rotor is pointing right at the front most pick up and the trailing rotor almost straight back and just coming up on the rear most pickup yea that would be pretty close to 20 deg. to change that the trailing vacuum advance can be moved but I wouldn't suggest you do that .. I'm also not sure if it is 0 deg on the leading timing .. the pickups are about 180 apart but the trailing rotor and pickup is only 20 deg from triggering the trailing coil .. As soon as the front rotor goes past the front or leading pick up the rear or trailing pick up will fire the trailing coil .. they are not exactly 180 the rotor is 180 but the trailing pick up is more like 200 deg that is where the 20 deg comes from . j9fd3 is right it isn't 180 but in the cap it is not exactly opposite

 

that's not 180!

also since the distributor turns 50% of engine speed, actually every distributor does, the distributor fires all the plugs in 360 degrees, and the engine takes 720

anyways since the distributor turns at half speed, the pickups aren't 20 degrees off, its 10.

 

That's also why there are twice as many points on the reluctor as there are rotors in the engine... because of the half-speed rotation of the dizzy.