There's a power wire to the antenna and the central locking pump but I doubt either is rated for 20-30 amps continuous.

If you're wiring a stereo amplifier or a WVO heater, use dedicated wiring with dedicated fuses. A wiring kit for a big amplifier should handle that load.

You can route wires down the door sills to the back seat, then up behind the seatback into the trunk. Protect wiring where it goes through the bulkhead.

Sixto
95 S420
87 300SDL