Slant Six in trouble

Sounds like a timing issue esp. if your idle is the right RPM. double check your firing order, make sure your spark plug wires are good, cap rotor, if your running points those too, condenser. A bad carb will make it idel rough, run too lean or rich, hesatate on take offs & some times can cause pinging while climbing up hills due to un-burnt fuel.

Hope this helps!
Jeff