Slant 6 intake/Exhaust Install

What are you guys typically paying to have your /6 manifold milled flat? I need to have that done myself. I would have adjusted but my INT/EXT mating bolts were just about locked solid so I took a chance and put it back on anyway. Lasted about 1000 miles before the leak got really bad. I've got to fix it before putting the Dart out on the road again for the year.