Im restoring a 86 ss and only the tach filter is mounted on firewall with no wires exiting it to the dizzy, im painting the firewall and wondering if filter is necessary. What does it really do no motor in car at this point so easy fix now. Thanks in advance

Here's an explanation to what that tach filter is supposed to do. And the tach filter in the Monte is the same one that was used in those Vettes. Do you need it, maybe, probably. The stock tachs in the monte have their share of issues. They are only a 2 wire stock filter. One end to the TACH output on the distributor, the other to the tach input.
http://www.marshallinstruments.com/products/9219.cfm
Bob

Thanks Bob I appreciate your feedback and the website to purchase is a plus because I couldn't find one for Hei online in my search