parked me van up to mess around with it for about 3 weeks. when it stopped it was running fine

i decided to change the dizzy and rotor arm coz the old ones looked done. after swapping them over i tried to start it. it now turns over and then lets out a shotgun sounding backfire and then nothing

i tried it with the old stuff back on but same problem.
i followed the haynes manual diagram when connecting up the LT leads just to be sure. any ideas

Why pay someone else to fix it for you when you can waste 2 months doing it yourself!