93 Chevy c/k 1500 4WD V6 - electrical

My running lights, instrument panel (tach) light won't work. My brake lights and reverse lights work in the back. I checked the bulbs and they are fine. The instrument panel light has been on and off for awhile but the tail lights just went out recently when I hooked up a trailer for the first time. When pulling the trailer home the running lights on the truck and the trailer would flicker on and off until they finally went out. I removed the trailer harness from the main electrical system thinking there was a short but thast didn't solve the issue. Checked all the fuses and they are in good shape. Any thoughts? Is the instrument panel light and the running lights on the same circuit? Would it make sense that the running light circuit could be shorted while the circuit for the brake and reverse lights is still valid? Thanks in advance.