Well I learned some stuff about my 1970, 455 Buick Rivera's fuel system today. I was told and thought it was originally a mechanical fuel pump,
It was not. Both my car and the 69 & 70 Buick Grand Sport or GS as they called it, came with the 455 big block motor which needed more fuel them the mechanical pump could handle. So those cars came with a in tank electric fuel pump, which was a first for them in those years, the motor's were I identical. The problem is no one makes or has parts for these fuel systems anymore, because they were rare in the first place. Someone had replaced the Fuel sending unit in my tank at one time because it was not big enough to cover the opening in the top of the tank, so if you went around a corner or down a steep grade gas could leak out of the tank, not good. I guess it's all after market high performance fuel system stuff for her from now on.