I can't say for sure since my 76 is carbureted, but i have a 94 Camaro Z28 with what appears to be a similar plug. My plug is meant to test the fuel pump. I can apply 12 volts to it and the fuel pump will run. I'm guessing your TBI may have something similar.
I just went through this puzzle a year ago....
I have a 76 (16 GAL tank) and a newer bed with a fuel door. (Not sure what year bed as the truck was in pieces when I got it). The filler opening on the bed will tell you if it's a 79-83 or 84-87. LMC catalog is helpful with pictures. I have a...
Which brand lowering springs did you use (I don't know if it matters)? I have the CPP Modular drop spindles also, but I cut the original springs down some and it's not enough. Not sure I want to cut more. Yours sits perfect.
Thanks,
-Greg
I got new ones from Rock Auto. There are two sizes available, 1/2 inch or 5/8 inch. My 1976 had the 5/8 inch ones. You just have to measure the diameter of the holes.
I have been putting a 1976 C10 back together (I did not take it apart) and I was able to loosen that drivers side hinge bolt from the left most AC vent. I did not have any wiring or air ducting in the car. I was able to use a 9/16"? deep well socket and a short extension with an adapter to a...