So only help I can really be is to say change the positive cable to 1/0 or 2/0 to get the absolute max amperage and voltage to the starter and don't use dinky ford solenoids get a nice big boat solenoid around a hundred amps for the wire going to the starter solenoid and use as big of wire as you can that's like 4 gage and fine strand wire. GM way under sized the wires.
Already swapped out positive and negative to 1/0 cables, both to the starter and the lines tying the batteries together. I also have the body power feeding off of the driver-side battery so that current isn't going through the starter wire anymore. Cranks way better now.
The starter solenoid wire is...umm...4 AWG? I think? I don't remember off the top of my head. But it's heavier than stock.
And the solenoid is rated for 1500amps, so we should be good on that front...









