Donhamilton76

Hello, we are working on a 72 cutlass that being cloned to a 70 442. The previous owner installed dash and engine harnesses for a 1972 442 and we are installing the rally gauges. I know each year harnesses are different etc. but he does have the front and rear lighting/bumpers for the 70 model. Here’s my issue:
everything works properly until you turn the exterior lights on. When you turn them on the fuel gauge seems to be getting 12 volts and goes to empty. I’m not sure if it’s the light harnesses or the pins needs swapped. I have the picture for the pin locations from this sight. Before I swap I was checking to see if the light harnesses may be the issue as the gauges say 70-72 but not sure how they can be. Don’t want to fry anything so I’m asking for a little info from someone who may know the electrical systems on these better than myself!

also not sure if the light harnesses are 70 or 72 that go to the pigs for the light! Thanks in advance!