You can isolate the problem with a digital multi meter....
Disconnect the column harness connectors and test for continuity from the pinout on the plug to a chassis ground location in the cab... if the wire goes from the column... to the 1157 bulb and into ground.... you will see continuity... (my multimeter throws a tone)...
You can then see if all 4 corners of signal are 'correct' and than can either isolate the problem to column wiring, or to something still within the fuse panel or the wiring to the 4 corners itself.
Turn signal relays replaced or tested good?
Are you running any LED turn signals... the will not work without an LED turn signal relay(with ground lead)
PS: I know your pain (LS swap the same time I redid the entire chassis harness)
Use a test light on the horn relay feed wire vs. feeding it thru the relay... you may need to replace the horn relay if it was burned up when it got stuck on