Gas guage not working after cluster swap

[noisemachine]

Hi guys, new member here. I just swapped my dash cluster out for a tach cluster that is original (not repop) but was cleaned up by the guy I got it from with new lens and bezel, so it has been apart. Now my gas guage is not working and the needle stays at 2-3 o'clock. All other guages and dash lights work fine and everything worked on my old cluster. I do not think it is the sending unit as I have no power (with key on) at the fuse block terminal where the brown sender wire plugs in. I have not had a chance to check anything else yet so I thought I would get some pointers from you guys. The truck is a 70 C10. Thanks.