Magnum oil pump

I tried replacing the oil pump with a new one .melling #m-72 . When installed the oil pan would not sit flush and kinda hits the oil pick up tube . It’s on at the tightest and sitting leveled. When the original pump is on it sits flush . I cross referenced the Oil pump (M-72) and it pretty much is the same oil pump for small blocks . Anyone else have issues when replacing the oil pump? I suspect the original pump is still good still have yet to open it up and check tolerances. I had a new oil pump laying around from a previous build that didn’t workout just hate to have a fresh part just laying on the shelf. Any feedback / suggestions/experiences are appreciated thanks in advance.