This has me confused. I have a wrecked 1987 Blazer that I am pulling the 350 TBI and transmission and putting in my 1990 Jimmy with a bad m350 TBI and tranny. In tearing down the 87 I have found two oil pressure senders - one in a port directly above the oil filter and one near the distributor. I have looked on my 90 and my wife's 91 Suburban and both only have one. Also, both the 87 and 90 have factory oil pressure gauges. The other thing is the one above the oil filter only has a spade on it not a GM weatherpak connector but it does have the corrugated covering and does go into the wiring harness. So how many are there supposed to be? I have heard of a oil pressure switch for the TBI, but where is it? The one near the distributor only had two connections in it. So does the gauge and the computer use the same sender and if so, how does that work? As you can see I am really confused on this one. Any help will be greatly appreciated.