No Spark help

Why are you measuring voltage at the coil?

If there is voltage drop from the battery to the main splice, then find that first.
If there is a voltage drop from the main splice to the ballast resistor, then narrow that that down.
If there is a voltage drop to the coil its hard to know anything 'cause current is flowing through the resistor and when the distributor is turning its being turned on and off!

As far as grinding terminals go - I don't know. You'll have to be the judge of that. You may have to adjust the female terminals if you've thinned the males.

When there is a drop, you have to junction to junction along the current path until you find the location(s) of resistance.

As far as spark goes, check the coil wire is seated better than in the photo, and preferably find a coil that is in spec.

You'll have to buy '74 FSM. In the meantime you can piece together information using the '73 along with what you find from other sources about '74 including what you actually find on the car.