HELP ..Runs dies No start .. then start

Have you considered replacing the connector? The main red wire looks like it got hot once (insulation is a bit wrinkly), there may be bad connections inside.
1974 DODGE DART 5.2L 318cid V8 Ignition Control Module (ICM) Connector | RockAuto


also measure the OD of the pins on the new vs old ECU if the new ECU is smaller in dia that would result in no contact and could be the reason new ECU fail.