having startup issue

im having a issue after driving my 74 duster /6 , if i shut it off and try to restart there is no spark but engine will crank.... ive swaped parts from my 74 scamp as it has same parts.. ive swaped ignition box, voltage regulator, coil. and replaced balast resistor.. what else is there im missing anyone can help please and thank you

matt
IEduster
what you have missed is the $15 mag pickup in the distributor. yes coils come and go, and yes ballast resistors are a pain, but you said yourself you switched everything else.

the mag pickup will come and go, you'll start 15 times in a row and time 16 you'll crank and crank with no spark...then next day it'll fire right up....ballast resistors just cook and die, they won't come back.