wiring harness

looking for some suggestions..i have a 68 dart 270 car that i have changed to 340 engine and i am working on the factory wiring.i recently replaced the underdash wiring and everything looked good and went right in place ..i purchased a under hood kit and it had been modified for electronic ignition which i have added and everything went in place except the horn and side marker lights which i was going to lengthen. but when i powered up all i got was tail lights and none of the fuses had power..i think my trouble is with the underhood harness which i now think is for a 67 dart . .so far have only found a used harness from a 68 6 cyl dart..will that work? found a after market harness for 170 or i can lay out my old 6 cyl harness that is cut up and try to make it work..any idea or suggestions is appreciated.thanks