Anytime you change things from stock, you can count on having to modify something to get things to fit and work properly.
Those oval shaped pieces will have to be massaged to fit correctly. File or grind down the underside to compensate for different thickness of the two manifolds. If memory serves, there are two different sizes of those clamping pieces. Four are the ones you describe. Two of them are about 3/4" longer and the hole is off-center. With my Clifford intake, I'm using six of the shorter style because the manifold is fatter all around. When I first put the headers on, I still had the stock intake and I don't recall what combination of pieces fit at that time.
That brings up the studs. I may not have explained that very well. There are eight threaded holes on the manifold surface of the head. The first one is in front of #1 exhaust tube. It has a locator pin in it that stands up about 3/8". Soak it with penetrating oil for a couple of days and thread it out with a real good pair of vice-gripes. Same with the one behind #6 exhaust. The second hole between #1 exhaust and #1 intake should have a factory installed stud in it. The same with the second hole from the other end of the head. For whatever reason a lot of the head rebuilders remove them and do not replace. The other four holes used bolts. You want to end up with eight studs IMO for the best results. The end studs just need a good fat flat washer.
I was in no hurry to put the headers on. Every time I stopped by a wrecking yard, I would look for a 250 and usually would find a couple studs and hardware.
In this photo there is not one nut holding the manifolds in place. They are just sitting on the studs. Even the rockers are just sitting there. After getting the head on, I was anxious to get a look at what was to come.
It isn't a great picture, but you can see the stud in the last hole.
[img]http://www.home.earthlink.net/~roadruner/MyEngine.jpg[/img]
If you're wondering about the rockers, take a look at the valve cover. I cut the corner open and added a section. You would never notice it, without it being pointed out.
