this is a dumb question, but can i just pull the fuse for the tpi fuel pump, and still use it as a pick-up, and run a mechanical fuel pump for the carb and use all existing lines?

use the tpi pump and run a mallory #4309 regulator instead.

There is a 50/50 chance you can pull through the pump. I tried it once. Chances are you will get vapor lock. While you are driving you will starve your motor and it will just die under acceleration.

You have two choices.

Drop the tank, remove the pump.

or use a 3 port fuel pressure regulator.

If I were you, I would use the electric pump, reason being. Adjustable regulator allows for easier fuel tuning, also you can add a fuel pump cut off switch that makes a great anti-theft device.

In a word NO, the pump will pose a restriction that will severely limit your ability to make HP, as for how to run the factory lines you can either drop the tank and run a line to the bottom of the tank and run the engine mounted pump like you suggested (which I consider the proper way and safest) or you can run a bypass type regulator but if you go this route make sure you have the proper lines (either solid dubble flare tube & fittings) or AN type fittings with the proper high pressure lines not just parts store rubber line and hose clamps, the factory pump will be putting out more pressure than would be safe to use the standard hose and clamps, also regulators that will work with the TPI pumps pressure are generally expensive to handle the high pressure that TPI uses it's your choice just do it right..