In all the 3800 swaps I do, I only wire up the oil pressure sending unit to the dash gage and nothing else. You certainly DO NOT want to wire up the oil pressure sending unit to the fuel pump wiring IF you are using a high performance fuel pump as it could burn up the switch contacts in the oil pressure sending unit. An OE-replacement type fuel pump should not overload it though.
The only reason why GM used the oil pressure sending unit to help power up the fuel pump as a back-up was because for a time, they were using non weather sealed relays which proved to be unreliable. In all the Fiero swaps I do, I change the relays over to the newer weather sealed style and omit the oil pressure switch fuel pump wiring. Never had a problem nor heard of a problem.
By the mid 90's, GM quit running the fuel pump power circuit to the oil pressure sending unit themselves anyway.
-ryan
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