Just some random thoughts:
Electricity is like water, it's lazy and follows the path of least resistance. The more grounds, the better.
Hot start conditions (on street engines) can be overcome with a vaccum advance pot. A 10 or 20 degree pot will take out enough timing to get you started, then put it right back in once it fires. My SBC likes to idle with 38 degrees advance! So in order to get it to start everytime, I put a 20 degree pot on the distibutor and 18 degrees initial. Use a vaccum gauge and a dial back timing light to fid what works best for you. The more vacuum it has at idle, the "happier" my engine became.
Your results may vary.
Also someone mentioned the condition of cables. Borrow or buy a multimeter. Test a new battery cable and see how many ohms of resistance it has. Then check yours. if the reading is substantially higher, change it out. You may see the change right there.
Again think about a garden hose and water with regards to cable size/gauge. If you can swing a bigger/thicker cable, go for it. It is easier for the volume of current to pass thru a larger gauge cable than a thinner one. Just like you can fill a bucket faster with a 3/4" dia hose that a 1/2" dia hose.