typical fuel gauge/instrument cluster question

Thanks for doing some guesswork - I probably wrongly assumed that early a-bodies were generally the same in that regard. It's a 64 plymouth barracuda.

I've pulled the cluster and bench tested it with a 12v supply - I get the same slow response on the gauges directly.. unfortunately, the 64 has the IVR in the actual fuel gauge. A test light shows the strobing and I'm getting strobing ~5v, but I don't really have a sense of what kind of regularity or rate I'd see out of a mechanical limiter. When you say "pegging", I'm going to assume that doesn't mean slowly crawling upward over the course of maybe 10 seconds? Thanks for the help.