Another interesting thing I noticed...
In the 1969 Assembly manual the part number for the PS Pump is different for the L6 and the V8 engines.
L6 calls for pump #7805653 Pump Asm.
V8 calls for pump #7805656 Pump Asm.
V8 w396 calls for pump 7806370 pump asm.
This is all found in the N40 Section.
The picture of those V8 pumps are illustrated with a design shape that wasn't used until 1975.
I really think the PS pump was redesigned for the 1969 Small block heads with the accessory holes.
The newly designed pump was produced with a new plastic cap.
The listing application does not show a separate part# for the cap, so the caps were likely already attached to the pumps when delivered from the manufacturer.
The P&A book listing # may only be for the replacement items if only the cap was needed.
So it may be very likely that SB V8's 302 350 327 got a plastic cap and all others L6 and BB V8's 396's 427's got the metal one.
Or the pumps may have all been shipped with metal caps untill the supply was used up.
Just "thinking out loud" here, with possibilities.
Somewhere is the internal memos to prove what happened. Someone has them, we just got to find them.