Rally Dash Conversion Question

Hey all, I’m currently converting my 1972 duster to a rally dash using a 1967 dash. Before I start I suspect I have a bad fuel gauge or the voltage limiter is no good within it. When I start the car I get no reading on the fuel gauge, oil or temp but on the back of both pegs on each gauge I get 12v. I also need to replace my sending unit not sure if this would have an affect or not? Hoping someone has a suggestion thanks