I found some old SPI gauges laying around without any senders... I'm pretty sure I won't be able to find the specific sender anywhere for each gauge since they are out-dated... So my question is if anyone knows whether or not any other sender will work?

 

need to see a pic of the back to now it u can use any other sending unit

 

I don't see how seeing the back will help... Each one only has four wires coming out the back... If you need to see a pic to help me let me know and I'll put one up.

 

you need to find what the corresponding voltages are for the gauge and then find a sending unit that matches it