In 2013 Palo Alto Speedometer refaced my 914 gauges and built me a 4 gauge combo unit.
I didn't like the fuel sender that came with the combo unit so I replaced it with a Karmann Ghia tube type sender.
Unfortunately, the resistance range of the tube sender was different from the original sender and the fuel gauge accuracy suffered.
Palo Alto Speedometer just recalibrated the fuel gauge to match the tube sender.
They did this at no charge, not even for shipping it back to me.
This is excellent customer service.