Can't actually answer your main question, but I'll address some asides .

1) The 300D turbo never came with an idle adjustment cable.
2) The '76 300D IP would probably work, but it would really limit your power... the turbo IP delivers more fuel than the NA IP, so reverting to the NA IP would make your engine perform more like a NA engine (~90 HP v. ~125 HP).

__________________
"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."