its considered a "center" sump; pan (tho the sump ain't exactly centered). front/rear sumpers are all forward or all rearward. for a quick visual drain plugs are traditionally at the rear but not even sure if that holds with these. I will go check mine again & the 451 block is belly up so I will drop it on there. I know it was the opposite of what the guy sold me (I dont even think he knew he was wrong) however I feel lucky!.