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You have to pull the engine, or pull the transmission out, and then lift the engine up enough to get oil pan down enough to clear oil pump pickup inside the pan and slide it back
Many forget about the oil pump pickup sitting at the bottom inside the oil pan, that's the reason you need the clearance.
If you pull the engine up high enough you can drop the oil pan straight down, if you pull the transmission(and flywheel/flexplate) you can slide the oil pan back but still need to lift engine up so pan can drop down enough to clear oil pump pickup