Well for coolant gauges you have a couple options (stock depending). This is a drop in replacement, but will read 15-20* higher than reality (though that has no effect on the coolant overtemp sensor which will still work properly if its too hot)
WI - Temperature Coolant Gauge MEP-802A MEP-803A 804A MEP-804B MEP-805A MEP 24 volt
This is an inexpensive alternative for a coolant temperature gauge for tactical quiet series of generators (GENERATOR, 5KW, 10KW, 15KW, 30KW, 60KW TQG, TACTICAL QUIET FAMILY) which include the MEP-802A, MEP-803A, MEP-804A, MEP-804B, MEP-805A, MEP-806A, and many others. The gauge in this listing...www.steelsoldiers.com
I have also personally used the DATCON 101587, but I don't see it available anywhere.
The one in the classifieds will work here. If you wanted it to be spot on, I am sure you could get the info from Beede on the resistance range and a suitable sender replacement... but it will work as is.
101586 - Datcon Water Temperature Gauge 24V 100-240F - 101586 - ALL Datcon Products - Datcon - automotive gauges - Vehicle Controls
101586 - Datcon Water Temperature Gauge, 100° - 240°F, Electrical, 24V, 2 1/16' (52mm), Black Bezel, Style: Heavy Duty Industrial
vehiclecontrols.com