Engine issues

So today i took the dart to the power wash to spray down the engine bay after doing so and changing out the starter now the car has a horrid miss. I covered all the ele. components the best i could before the bay was sprayed down. If you give the car any kind of load at all it dies. Such as even trying to accelerate forward or reverse in gear. The car stumbles and dies the car will fire up again but its not running as smooth as it was before i did the spray down. I just changed oil on the car which it needed it and also changed the fuel filter. Im going the change the plugs as well later today. I put a different voltage reg and ign box on the car a few days ago because the factory ones were still on the car (30+ years old) and all the rubber/glue on the back of the boxes had melted. Btw the car is a 1976 dart sport 225 slant 6 i picked up last weekend it seems to have been sitting the last 4 years i put 4 gallons of fresh gas in the car.