The 6-bbl carbs are tricky to get right...That carb throttle shaft should have teflon seals on each side of the throttle bores...If they're shot or missing completely you'll have a massive vacuum leak from the beginning....But if the shaft and/or bore is wore too hard you're better off with new or sending them out... You can't go wrong using Harms...Scott does excellent work....I guess the ride back and forth from over there would be a factor going the rebuilt route