Yes, the tanks are different, but that shouldn;t be an issue going from TBI to carb, would be the other way.

You don't need to fool with the fuel gauge sending unit at all, it is separate from the pump module. In the picture, number 8 is the fuel pump module, number 9 is the gauge sending unit. they go into separate holes in the top of the tank.

All I would go is pull the fuel pump relay, plumb in a mechanical pump and see if it will draw through the in tank pump and feed the carb. One thing that did pop into my mind, your engine may, or may not, have the fuel pump eccentric bolted to the front of the cam, it probably does. If it does not you will need to add it. If you want to try to regulate down the in tank pump instead, the computer is what turns that pump on and off via the fuel pump relay. You would need to address that.

Ramcharger tank drawing