the 85 i own i just changed the one for the guage in the dash.. it is the second one.. not the first one.. easy way to make sure is take a paper clip.. make one end stick into the female plug and ground it.. if the temp guage spikes youve got the right one..

oh i misred your post

but the one for the guage is on the driver side of the block.. and on the 85 their are 2 sending units there. one for the gp relay and the other for the guage... read what i posted and you will find it