I believe your second pic is of the turn signal mechanism that someone replaced the lever with a screw.
On your battery isolator, I'd recommend a charging relay to the auxiliary battery that closes only when the ignition is on. The items fed by the aux battery can be isolated from the engine completely, with just that charge circuit active when the engine is running. My daily driver truck uses that arrangement for charging the camper battery (or trailer battery if I had one.)
The starter switch can be replaced with a repop or NOS switch. They do tend to take a beating.
