Gauge issues

[HiredGun]

Recently I was given my 72 CST. It was a barn find and had been under a tarp for over 15 yrs. That said I knew it wasn't going to be a simple project. Got the truck up and on the road in about 3 months, but without a working tac or fuel gauge. I've been reading around on here and from what I've gathered, the "tan" wire is from the sending unit and that pretty much acts as the ground for the gauge and all the gauge is reading is how much of a ground it has as the float moves.

1st off, the TAC:
I connected the wire to the distributor. when I put my lights on the gauge lights up (sometimes). I'm thinking thats a simple ground problem. I found a wire that came from the tac and is a male spade clip (all probably rigged work from my grandfather as it was his old track truck). I found a weird clip from the wire harness that clips on underneath the dash. I stuck the spade clip between that clip and the dash and the gauge reads under 1k rpms but nothing else

2nd, the fuel gauge:
NOTE that I have a plastic tank from either a Blazer or Saburban complete with a brand new sending unit. The unit has a port that sends the signal to the gauge and another that you ground to the frame I'm assuming? I've ran wire along the frame to the fuse panel. The gauge has always read "over full". And I dont have a meter to check this.

I see me very shortly removing all the wire harness and starting fresh