Need help understanding Mopar ignition…no spark

There are E core coils.......& there are E core coils.

It HAS to be compatible with the ign system with which it is being used. The MSD #8251 is an E core coil, but it has a primary resistance of 0.04 ohms & is designed for MSD 7 CD ign. Not for inductive ign, like HEI.
The GM HEI module has an inbuilt current limiting device to limit current to about 5.5 amps; the original GM coil had a pri resistance of about 0.6 ohms.

The coil needs to be compatible with the ign system it will be used with. Not a case of pick-a-coil.