360 Running Issue(s)?

If not fuel, then spark. Install a "spark tester" in series with the #1 plug. Cost ~$4 at Harbor Freight or much more elsewhere. You should see steady flashing of the neon bulb. Also try a timing light and see if you get a steady flash.

Did you try the basic electrical hookup that 273 recommended? My guess would be a bad ground to the ECU body, but could be the ECU itself, a bad key switch, bad bulkhead connection, or erratic ballast connection. I don't see how bypassing the ammeter would help this problem. Run a 12 awg wire to coil+ from the battery to bypass all the supply wiring, but for <1 min or the coil and/or ECU will get hot.