i don't know the exact date but probably sometime in the early 60's the feds mandated radio suppression wires on new vehicles. back in the day, late 60's for me, we yanked the suppression wires because they were unreliable and had a lot of resistance. there is some fairly good suppression wire out now that wasn't available 5-10 years ago. i've been making my own wires for over 35yrs; hard habit to break i guess, .