you could count on the chevy 350 starter drawing in the neighborhood of about 250-350 amps depending on the starter used and the performance level of the engine.
for a 250-300 amp draw over a max 4 ft length you need a 4ga cable minimum. welding cable is great because it is more flexible due to the number of strands. a starter/alternator repair shop should be able to fix you up with the cable with the lugs pressed on and shrink tubed for a good price. I am not a fan of the cheaper cables that a lot of auto stores sell, they don't flex well because they have less strands plus the insulation used is also less flexible when you go to strip the cable for a terminal install.
I like to use a ground cable from the battery to the engine block and one from the block to the frame, large cable. a smaller cable should go to the body depending on what the amp draw of the accy's used will be. longer cable runs mean larger cable to handle voltage drop over the length.
https://www.crutchfield.com/S-BnuZ5p...uge_chart.html