Wrong fuel pump? Lower pressures?

[WestButteTruck]

I came to the conclusion I needed a new fuel pump. Went to parts store and was given a new pump. It looked the same, but when I fired it up, it seemed pretty obvious it was not pumping enough gas. Ran very poor, and had no power at all. It wouldn't even keep my clear filter half full. Anyway, I do some looking and they make a pump for a MT and an Auto. IF I got the one for the MT, would that make a difference if I have the Auto? Higher fuel pressure? I wouldn't have thought it would make a difference. Anybody have any ideas? It's a 72 with a 350 A/T. Will see about taking it back tomorrow.......if they let me.