I'm not sure of the angle but I know they should be as close to the wheels as you can get them.
Here is the link to the build I was talking about it wasn't on here.
http://www.pro-touring.com/threads/103642-1997-C1500-Autocross-Build
That's a cool build!
He used an Impala rear-end. I thought that they were wider than the GMT400's. No mention if he narrowed it or not. Like the idea for that, though. Has the upper mounts for the links already cast into the housing! And...no need to hokey up some kinda rear disc brake set-up!
To the O.P.
What size of tires & wheels are you considering? I've kinda been keeping my eyes on what the auto-crossers do to their vehicles with the idea of maybe casually competing with my '98, once the LS is (eventually!) installed. I've noticed that not many are using the big 20"+ wheels. Usually they are in the 17/18" wheel size. Just enough to clear larger aftermarket brakes. Those big wheels are just to heavy. That extra weight makes for slower acceleration, & longer braking distances. But, especially important in auto-cross, they are harder to get to change direction.
Then, there's this! (ooohhh!!!) This truck is used for Auto-cross.
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