2000 chevy tracker blows 60amp fuse as soon as battery is connected every time. But if tail lights are removed it seems good . One other thing after market radio is installed but idk how correctley.

You already know the light (or Tail light) circuit has an issue grounding out.. But someone might have "wired" the after market radio into it, One of the most common issues are after market alarms and after market sound systems wired in by SOMEONE who has no clue. start searching for wire splices use a multimeter to check each circuit.

I just saw a video on YouTube where a guy dropped the gas tank thinking he needed to replace the fuel pump. What he found was salt off of the road created a hole in the fender well that allowed water and salt into the area where all the wires are located. That caused corrosion in the connectors that led to wires heating up and burning due to the high resistance. This was on the driver's side behind the tail light. You might have wires that are now loose and grounding out in that area. The video https://www.youtube.com/watch?v=Bv_CbQERnzg#t=577.13526