Sounds like the wires could be on wrong. Check the firing order.
If you had the magneto off. The magneto will need to be timed to the engine. Get the engine on top dead center number one cylinder compression stroke. Then turn the rotor inside the magneto to the number spark plug tower. Should be ready to install.
I think the model C Wico doesn't have timing marks on the rotor drive gears. The internal gears could be timed wrong.
I too would look for a Wico X series. Much better magneto. The Allis Number is XH3001