What cable size do I need?

I'm getting close to fitting a battery and turning over (and maybe even starting) my 'stang, but I have no battery cables to copy.

What size cable should I use? I'm guessing the +ve to the starter solenoid, the starter solenoid to starter, the -ve to ground and engine to chassis should all be the same size.

On tiny engines like we have over here, I would normally use a 16mm^2 cable, but for a 289 I wonder if I need something bigger. I can work with American or Imperial cable sizes.

What do you guys advise?