The temp gauge on most of the Miliutary vehicles is electric... at lease it is on my M-38... I use to have a capillary temp sender but it came with adapters to let it fit...
The referenced electric sender types were 24 volt. Your M606 should be 12 volt. The capillary tube type sender was originally installed on the left rear side of the cylinder head in I believe a 3/4" pipe threaded hole. You may have to choose a different capillary type with a 3/4" pipe thread fitting.