I am trying to put an TBI from a 1987 K2500 in a 1986 K2500 with dual tanks, I have a donor vehicle but some one has removed the fuel selector valve from it and turned it into a single tank donor. I have the dual tanks on my 86 and from what I can tell the selector valve are the same from 1981-1989 so no problem there but what do I need for a electrical switch to swap the fuel gauges and also switch the fuel tank pumps as I have the in tank ones from a 1987? I also notice in the LMC book that the dash switch is different in the 87 but have that also. I was wondering if the electrical swap took place in a switch mounted under the dash or on the fire wall? Also what do I need for wiring the two tanks together as I said they converted it to a single tank? Does any one also have a wiring diagram for the 1986 and 1987 trucks with dual tanks or where to get one? I have a Chiltons manual and a Hayes manual but neither have a diagram for a dual tank setup.