75 Dart /6 wont start. Electrical?

Start over and re adjust the valves. There are several threads about the procedure, some while running, some while the engine is shut off. Heres just one thread for example.
help-setting-valves-on-a-225.100536

If you try and adjust them without a fully warmed up engine add .003"ish to the factory gap to get it close. Then fine tune after you get it running. Just a couple thoughts there has been a couple threads lately about ignitions firing when cranking but not having power when on 'run'. Verify you have power to the ignition on both crank and run. Also verify that the rotor is at TDC on the power stroke when its on number one.
Do you have sufficient fuel pressure to the carb? Is crap clogging the fuel pick up and or filter?
Is your carb clogged?
When I got my slant the seller claimed it was in 'just jump in and drive anywhere' running condition. The fuel tank had crap in it, the fuel filter was clogged, the carb was clogged, and the distributor was off by one tooth.