Ignition dwell and adjusting it.

Abodybomber said
AND with that : If the one you have fires , try it . The quality of ignition parts for vintage parts ,have gone downhill. Might think about a Pertronix 1 conversion, or one of these...

Converts a 4 pin GM HEI module, to fit a stock Mopar small block distributior.
Also look at Greg / " Trailbeast " 's system conversion. It doesn't look stock , but it performs better.
The best part about Trailbeast : He just did a mild Magnum 5.9 /360 swap carbed .My thoughts are there . Have a good weekend.