OK, since you now at least have 12V to the amplifier, it is time to do some more troubleshooting. Disconnect the blue wire from the coil, unbolt it from the motor, and rotate the whole thing to unscrew the spark wire from the distributor cap. Now, remount the coil and reconnect the blue wire. Rig up a spark gap off the end of the spark wire.
Disconnect the wire between the amplifier and breaker points.
Turn key on, double check your 12V input, then lightly brush the wire from amplifier disconnected from the points across a bare metal grounded part. You should get a flurry of sparks across the spark gap. If you do, you know the amplifier and coil are at least good enough to work.
No sparks? Then you have a bad amplifier or coil or both. You decide which. 50% chance of being right or wrong. A new amp might come with a new coil anyway (?)
If you got sparks, check breaker points, distributor cap and dist rotor.