Keeps blowing fuses

[87Skier]

I just picked up an 89 4x4 2500 Suburban. I knew it had some issues when I got it. The main issue right now is that it keeps blowing fuses. The 20 Amp tail light and instrument light fuse last about 1/2 second when the lights are turned on.

The headlights, turn signals, brake lights, and interior overhead lights work.

I started troubleshooting but I'm a little lost where to go now. I disconnected the front and rear wiring harnesses and it still blows the fuse. The instrument fuse is in tact and hasn't blown.

Any ideas where to go from here?