Keyless entry power door locks review.
I bought one of these for my 70 300 a couple years ago.
Directed Avital 1 Way Security System | eBay
I then used Spal door locks for the doors and used a power trunk release from an early eighties Mopar. The door locks bolted right up to the existing holes in the door frame. I've wired a time delay relay into the system so the interior lights up when you hit the remote. Parking lights flash when you lock/unlock too.
It has worked flawlessly since the installation.