Registration and Posting Agreement
Assuming it's the 1987 in your signature.The oil gauge sender wire is Tan. There should be an oil pressure switch for the fuel pump as well.
Look down by the oil filter.
the two wire one will look like the oem one will be a couple inches longer but the same idea. they just changed the design within the past year. but this one is the back up
http://www.oreillyauto.com/site/c/detail/ACD0/D1838/03438.oap?year=1987&make=Chevrolet&model=R10%2BPickup%2BRWD&vi=5002896&ck=Search_oil+pressure+sensor%21s%21switch_5002896_3645&keyword=oil+pressure+sensor%21s%21switch#Won't this work?