Car wont start sometimes... need help.

hello everyone, i have a 1970 dodge dart swinger 340 4 speed that i am having trouble starting.
Recently i had a dual point distributor installed and now i am having problems getting the car to start.
Last year with my old distributor i could start the car fine every time i tried.
Now i can usually start the car first try after its bin sitting for a few days, i just give it some gas and turn it over.
so today i did that, it started fine i took it to the gas station shut it off and it started fine, i came home parked it in the drive way went out about 20 mins later tried to start it wont go... just keeps turning over. it has bin doing this to me most of the time when i take it out park it then try and start it again

If anyone has any ideas of what might me going on let me know please.
Also it still has the original starter if that would be causing the problem?
Thanks