So after checking my storage unit I'm pretty sure the tall pump (GM 3701562) that is on my buddy's bench is from my '54 261 block (no captain's bars) that was too far gone. The pickup is the "tub" type that bolts to the main cap rather than the disk type that screws into the pump.
The tub type pickup that bolts to the main cap and taller pump can be seen in the Installing The Oil Pump section of stovebolt's own 261 Rebuild page.
https://www.stovebolt.com/techtips/engines/261%20rebuild/lower-end.htmlThe Filling Station also sells the taller type pump for all '53-'54 cars and trucks and the shorter type for later 235/261s, if that means anything.
The disk type pickup that fits the Melling M-45 pump looks to be Melling part 45S2.
