I think I'd take the interior door panel off and see if there's a harness in there. If so, you should be golden. If no, ya got work to do, or you just go manual extension and call it a day. I've driven my F250 with the mirrors extended all the way out without towing. Make em' like a Ronco... just set em' and forget em.
OOPS! I misunderstood what you wanted to be power! You've got old school manually adjusting mirrors. THE HORROR
I'm looking through some diesel sites to see if anyone has a good writeup.
Yikes! I don't know if this will apply to yours but here's a thread
https://www.silveradosierra.com/threads/adding-oem-power-mirrors-windows-to-base-model.242242/