Cory, the diesel tach is a fairly uncommon item. It was only made for two years, and even then only the nicer optioned diesel trucks got them. I wouldn’t say truly “rare”, but there seems to be phases where everyone is looking and the price goes up. Then those guys find tachs and the market dries up... people trying to sell them say they can’t find anyone interested. I have a few now, I admit I am very much loosing track of my mental parts inventory.
It’s not just the red and yellow zones that make these different (although it’s the quickest way to identify if it’s the 6.9 tach). They are electrically very different and can’t be used on a gas engine. If plugged in while running it will stall a gas engine instantly.
SHORT BED 4-DOOR DIESEL: 1986 F350 4x4 under construction-- 7.3 IDIT ZF5+GVOD
STRAIGHT SIX 4X4: 1981 F150 2wd to 4x4-- 300 I6 close ratio diesel T19, hydroboost brakes, Saginaw steering
BIG F: 1995 F-Superduty under construction— converting to 6.9L IDI diesel ZF5+DNE2