if you got the sender listed for an electric gauge for a 235, it'll be "correct" for the 56+ gauge, but you have a 56 gauge, and a 235 with a 53 head? the 53 mechanical temp gauge had a sender bulb to fit the smaller hole, so the rating isn't the problem, it's making a sender fit for the later electric gauge - tricky .... there was just recently a
thread here discussing that, you need to find a way to adapt or change the head

Bill