When we were running the dirt track car, we had a single 0 copper strand welding cable with both ends soldered and shrink wrapped for both battery cables. We never had a heat sink issue. A 4g battery cable is too small in my opinion. I have #2 gauge cables on my V6.

Auto Zone should be able to test your voltage drop and amp draw on your car at their store.

A hot crank and start of a big cube motor needs all the battery voltage available. Isolate those cooling fans during engine cranking, grounding the fan relay through the op sending unit so the fans only run when the motor is running is a great idea. I was never happy to hear fans running 7 minutes after I shut the car off, they pull a lot of voltage out of a resting battery. Voltage needed to start the motor. Gene