That is interesting with the tires. I think the battery in the trunk is still a better idea. Putting the weight in the back and the 15 or so feet of 1 gauge wire is only going to be about 4 lbs spread out over the entire length of the car.
A 2/0 battery cable is about .5 lbs per foot. It's really insignificant. It may be as you mention about a 4 pound delta when all said and done.
Plus you can run the cable up the pass side which is beneficial in regards to weight bias. Out of the left front and moved primarily to the right side.
Chassis tuning with a GOOD shock is not a bad idea.
Converter would be another area to look at. I'd want something that flashes to the 4500 range and stays tight up top.