240 Fuel Economy Gauge
 

Is it possible to hook up an original 240 Fuel Economy gauge to a diesel?
Came out of my old '86 gas 240.

It will hook right up, and sit in the red at all times.

Possible? Yes.

Will it tell you any useful information? No. :p

Those gauges are operated by manifold vacuum, so unlike on a gasser where the gauge's reading would correspond to engine load, on a diesel it would just read zero all the time. Not very helpful.

It might serve to inform you when it's time to change your air filter, if you let it get really plugged, but you'd already know that by the loss of power and the black cloud coming out the tailpipe... :D