I have a number of salvage/surplus Monaco RV Diesel tachs - 5" / black face-white Numbers / 0-4k - only $39 plus actual shipping.
They are factory set to ECM style (12 pulses per rev) - but I include a simple proceedure to re-calibrate them for D/D "R" terminal use.
they work well on gear driven D/D 50DN 270 amp alternators (very standard eguipement on D/D) - but can be suject to belt slip on belt driven 50DN's
I also have Monaco Speedometers - 5" / black face-White Numbers 0-85MPH - requires a min 10k pulse per mile (Allison tranny style pulser (12 pulse per drive shaft rev) or (at least 20 pulses per wheel revolutions - like many GM multi notch (60??) front wheels)
Pete RTS/Daytona hawk_ii_mail at yahoo.com or 386...672..0571 Florida EST