An external pump is never my first choice, but in a 67'72 Chevy truck, it can be done with great success because you can get the pump lower than the tank, not usually possible with a frame mounted tank. That said, you won't want to have it try and suck fuel up and out of the tank, even though a siphoning effect it should work, it doesn't always work well. You really need to have the fuel gravity feed into the tank as fast as the pump can push it, so ideally it needs to come out of the bottom of the tank. Thats what I do when using the factory tank and my truck has run flawlessly for the last 52k miles.
Putting the pump in the factory tank will drive you nuts unless you are either deaf, or always drive with the stereo turned up to 11 all the time!
This is my build on my driver truck, has a lot of the same things you are asking about, throttle cable, factory A/C might be worth a look.
https://ls1tech.com/forums/conversio...71-c-10-a.html