My exp is with 67 and up. But it would be on the back of the cluster or perhaps internal to the fuel gauge.
Easy check would be to measure voltage at the posts on the back of the cluster, should be around 5 volts or so. I would not leave the gauges pinned for more than a moment or two as the heating elements in the gauges can over heat and do permanant damage to the gauges
That the way with me i have alway's had 70s car this is the first 60 model i have worked on and the only thing on the back of the cluster is a condenser think i might have it hook to the wrong post on the cluster.
