I'm working on mini tubbing on my Dart and have the spring boxes welded in. I checked the shackle angle yeaterday, using the holes that are in the frame, it is at 20*, about 1 3/16" top to the front. I also marked through the factory hanger, this would give it about 5/16" top to the front. This was checked with the cars weight on the spring.

Will 5/16" be enough?

Can the tubes that go through the frame be bought? If not I'll cut the old ones out of the factory brackets.

Thanks, Justin

You can make your own tubes for the upper shackle mount if you need to. I am assuming you have a welder, grinder, drill and a cutoff saw or similar, or a buddy that can help you out.
A piece of tubing, a couple of washers or a piece of plate you can drill a hole in and weld to the sub frame on either side is all you need. Shoot for 45 degrees, at rest. That will make the rear suspension very responsive. A little extra shackle length will also increase rise, if you want to increase the total body seperation under power. I made mine out of 1/2 by 2 inch flat stock, with a couple of extra holes to see what I liked best.

when i had springs on the runner, i had extra holes in the front to change ic height. did not get a confirm test with this. just an idea