Been there..done that. I installed autometer temp gauge. Several ways to do it..none easy.One method involves using a bolt that will fit the oem opening and tapping it to accomodate new unit. The method I used (real pain in the ass / but effective) involves cutting that bolt and tapping the treaded portion to act as a sleeve adaptor to the new sending unit. It gets a little complicated in that the sending unit supplied by Autometer is a fraction to large to go all the way down through the oem opening and into the water flow. Email me if your interested and I can go into as much detail as you need along with a few pics.