questions about battery disconnect wiring

Sorry I haven't been following the thread and missed a bunch of posts.
But here's a webstore I stumbled upon when looking for Packard 59 terminals
Lots of relays if thats what you're looking for.
CE Auto Electric Supply – Automotive Electrical Solutions

As far as rating. Figure if the starter power is going through it like shown in the top scheme (post 36) then it needs to be able to easily handle max starter draw. What's that? I don't know but the shop manual or the manufacture will list both 'normal' and max draws. A couple of hundred amps, not a 1000.

If going with the second scheme, then got to look at both directions on the heavier wire.
What is the max power that everything is going to draw if the engine is running on battery power? Say you have to drive it a while with a dead alternator. A car with points ignition is going to be like 3 amps maximum in the day time, plus a few amps for brake lights and turn signals etc. Probably no more than 30 amps with wipers and headlights etc. A car with EFI and electric fans is another story.
In the other direction, whats the recharge rate expected on the battery. This somewhat of a guess, but probably want the switch to be capable of handling at least 60 amps. I know that's way too high of a charge rate, but lets say a battery plate got loose and you need to kill the car. Whatever you choose, it seems logical the switch should be capable of handling more current than the maxi-fuse or fusible link on that line.