My 315 poly keeps running after everything turned off..

Here's what happened to me, when I installed a CDI ignition, into my Barracuda with the wiring harness from an electroni-ignition Duster.
Because the Mopar ignition switch runs thru the dual ballast in two different directions, when in either run or in start, To power up the CDI system, I had to throw all that out and bridge the start run circuits.
Ok so far so good, except in Run, the starter relay is now continuously energized. Not enough to cause it to kick the starter on, but current is running thru the coil at all times. my car has a clutch, so everytime I depressed the pedal, this grounded the Starter relay and so the starter would engage, engine running or not.
When the Ignition switch was turned to off, this cut the power to the relay, and the engine shut off just fine.
The cure for this was to run the Ignition amp off the battery with a relay on the fused start/run circuit, and IIRC I installed a diode on the starter relay to prevent it engaging in "Run"

The point is this;
you never know what just one tiny change to the factory wiring, will end up doing.
In my case, all I did was bridge the start and run wires, and "all hell" broke loose, lol.