You have a modern motor. Doing a "restomod". The answer is get rid of the ammeter (don't wire to it) . Run the alternator to battery as you said. Run everything from ignition switch and fuses. You can install a volt meter gauge or an annunciator light (My favorite)................. or neither. GM offered lights or gauges. Lights work for people who are not gauge watchers. Like 90% of the public. I always said give me the gauge option because I'm a man, a gear head, don't want no stupid lights. I never looked at any gauge except the gas gauge. When your truck won't start, you know you need to check the battery, the cables, then the alternator. Carry jumper cables and a cell phone.

Cable to starter from battery.
Wire to alternator from battery. Use a fusible link
Wire to ignition switch from battery. Use a fusible link
Fuse panel can have switched hot fuses and always hot fuses.
Sounds like you know how to do the ignition start and run circuit and lights.

The 3 wire alternator is really two wires leaving alternator. I.E. Battery pos post to Alt pos stud and blade 1 terminal to a bulb, thru bulb to ignition switch "ON" terminal.
Blade 2 is wired to alternator hot stud.

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn