69Custom,
The '83 trucks have an oil pressure sending unit next to the distributor. Looks like an upside down "fat top". The unit is screwed into the intake manifold. There is one wire connected to it. This wire runs back to the cab. I'm not sure of the wiring schematic for the fule gauage. I do have an original GM manual with diagrams. If could give me more details I could look at my book and try to give some more help.
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Gerardo
1983 Custom Truck
TX Plates: "BAD BOW"
http://www.geocities.com/abetterchemist/