Diagram , Photos connecting dashboard

1968 notch,

Most 1968 cars would have the "plug-in" Vreg in the photo (my 1969 Dart did). However, if your car has a tachometer ("rally dash"), then your Vreg is still inside the fuel gage (until ~1973). I doubt you could easily adapt the 3 spade box you have. I would take it back to NAPA, or if you lucked out and paid <$15, perhaps flip it on ebay since I recall they often sell for $50. The electronic Vreg works much better, unless you think a slightly pulsing needle is preferable (artifact of old thermal on-off control). Buy a "voltage limiter" with ring terminals ($30 ebay). You must open your fuel gage and disable the internal Vreg. I slid heat shrink over the wire-wound arm.

With an electric Vreg, you can adjust the voltage to get your fuel gage to read correctly at "E", or "F", or your temperature gage to read correct. Pick 1 of 3. My preference is knowing exactly where "E" is. There are other mechanical tweaks on the gage, but a bit tricky. I added resistors to fine tune all 3 readings.