There is a 76 on ebay.Will they interchange?It doesnt have the vent tube but I can make that work.Mine wasnt working.I replaced the float and now it pegs the needle on full.Any ideas what could be causing it?In case I could fix mine.It did look a little crusty.

pull the blue wire off of the sender stud & if the gas gauge drops to below E (key on) then yes it's a sender prob. See if you can retrieve the recent threads on new senders not reading correct (alot of reported innaccurate ones) so you can up your odds of getting a good one. Actually I think I'd rather have a good used one from an eBay seller w a good record (I'd want one that read correct then was pulled maybe to go 3/8"). I'd think a 78 and a 76 cordoba would use the same 5/16 OE sending unit. Might pull yours again & visual for where the windings are shorting as they are delicate & might have bumped or nudged them during the float changeout

As far as I know, they're the same except for 79's (smaller tank.

NOS are non-existant, best hope is to find someone on we crash who's removed a tank, and get the unit.

I used to have a couple used ones, but have let them go.

I would check at NAPA, I can still get a new there for my 70 RoadRunner.

Check your ground?

Disregard silly ebay fitment list drivel. The seller can plug in any data they want and, voila .

Two 78 PNs listed below for Cal and 49-state XS. Not certain what makes 76 different. 76 did not have a rollover valve but that's the tank itself.

If the ground is bad the gauge will stay on empty period.GM pegs if the ground is bad not a Mopar.You can un plug the sender wire and see if the gauge drops.Pull the sender and see if the resistor wire they use is screwed up.I had a bad sender wire in the 65 and repaired it.It was off a bit.Finally bought a new 3/8s stainless one for it.That and with the sender out check the ohms.That or hook it up and see what it does to the gauge moving it by hand.Just remember to ground it.Sometimes they can be cleaned with brake clean.Rocky