You are probably aware that an airspeed indicator is a differential pressure gauge. I made an LRI indicator using a 2 1/4" Falcon 0-80 MPH Airspeed. Use a loop of clear tubing to measure inches of water column. Just make a "U" with water in the bottom. Connect one end of the tube the to "P" input. Move the "U" so that there is 1/2", 1", 1 1/2", etc. difference in water levels in the tube. Tap on the Airspeed a bit so the needle will settle on the new reading each time. Write down the answers.

The front glass can be removed with a thin sheet of steel (1/32) cut to fit the grooves in the locking ring. Unscrew the ring and the glass comes out. Paint over anything you don't like of the face with flat black Testors paint. Put new markings on it with Florescent Testors paint (I used Green, Yellow, Red, White). Might want to practice a bit with fine brush 1st.

Put back together. Works just as well as the differential pressure gauge and mounts in a standard hole. I even put a light ring on mine.

Note it doesn't have to be perfect, it is just a visual reference.

Cheers,

Mark Napier