Topic: 1969 302 /351W Water Temperature Sending Unit with Gauges

[krelboyne]

Does anyone have a known assembly line, or NOS temperature sending unit for 1969 small block with analog temperature gauge? Ford number for the part is C9WY-10884-A. Cougar assigned number, ......... I know. But was used on 1969 Mustangs with F code 302-2V, and H or M code 351W, all with analog temperature gauges.
On one of the brass hex nut edges, it likely says Autolite 258 or 260 and an abbreviated date. What is the identifying color of the insulator?

The C6DZ-10884-B sending units have Autolite 260 and date. Red insulators on these I think.

Anyone know how to test them? aftermarket and C6DZ-10884-B sending units seem to give incorrect signals to the gauge.