A lot of D owners use an ACTRON Tach Dwell Voltmeter Model CP7605 to set their dwell. (Another for $22.99 total, used.) Like many others, you simply...
For the first part- When it is <15°C, the dwell should be 50-60° = 25-30° on 8-cyl scale, steady. Your's is 3° below the minimum. Given that, 1. and...