Firing problem

could be several issues. Wires not in correct firing order, cap not on straight or tight, no compression, weak spark from bad wires, wires grounding off on exhaust. Start with the simplest thing, make sure you have the wires on the correct plug. At night with no lights on start the motor and look for a spark between wire and exhaust manifold/header. Make sure nothing is keeping the cap from seating properly like a wire is caught under cap. Grab the cap and make sure it is tight on the distributor. look inside cap for a rusty film of dirt, you cap may be arching off. Problems like these are simple most of the time, just go over the basics.