It has to be a mechanical unit. GM didn't go to an electric temp guage until '56, then it was mid year on that chenge for the 235. However, the secription you give for the hookup for your guage is correct for a mechanical, the capillary tube kind of looks like a peice of bare solid core wire. Another clue is only 1 hookup at the guage. The electric guages have 2 leads, usually 18 guage, one for the power, and one to the sending unit. You might also notice a funny smell form the severed end. That would be the ether that originally filled the tube.
