None of the replacement petrol senders that I have seen have the plunger/float at the side. It’s meant to stop the gauge ‘fluctuating’ as the fuel slops around in the tank when cornering/braking etc.
The replacement I bought from Clade Renel isn’t to bad, but is only a guide and I still prefer to use the trip meter as a guide when to fill up 😆
BTW I did the same with my number plate lamp unit, (sprayed the inside chrome) but put 360 LED festoon bulbs in as they are far cooler and won’t melt the plastic lens, plus last far longer than the original incandescents