318 running bad

im new to carb'd cars, and mopar, so im hopin for a little help. i have a 74 valiant w/318. 150k on the motor. just bought recently and decided id tune it up and change the oil. the oil was old and worn, as were the wires and plugs. i replaced cap rotor plugs wires oil and air filter. i pulled the coil out to get the new wire to fit, but it still doesnt fit tightly. after this the motor ran fine for a day. now it seems to misfore and backfire. it hesitates when throttle is applied, and sometimes stalls. i know the wires are in the correct order, so what else?? any help would be appreciated
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