Found my dads original 1971 duster!

They can be taken apart. That's how you defeat the internal voltage regulator when you are installing a solid state IVR. Check out the link I sent you from RTE. They have instructions there.

Damn....Treed by @Demonx2 :)
That link looks like great instructions. For some reason it comes up very blurry on my end. Can’t read any of the writing