The B latch relay should be the third relay farthest from the firewall.
The ICM has the coil clipped on top of it.
If looking at the ICM from the driver's side of the vehicle, starting from the left a three pin connector, a two pin connectors in the middle, and an unused three pin connectors on the right.
The left three pin connector, from the left with assigned letters: C=Tach Signal, B=Ground(dipstick tube), and A=12v from ignition(through the B latch relay).
Check for 12v at "A" with the ignition on and a good ground through "B".
And yes, pulling the coil wire from the distributor cap and holding it to a good ground is fine. You want a BLUE hot spark.