When I replaced the front suspension on the wife's '06 Trailblazer in early June, I set the lower control arm brackets in their frame pockets as far to the rear (towards the tailgate) as I could and still get the bolts in easily. As regarding the side-to side placement, which will set the camber, I put them in so that at a point about 3" (I'm going from my aging memory on this distance, it may have been a bit more) from the front of the pocket the bracket was flush with the edge of the frame pocket. I used a small metal straight edge to get it flush. At a point about 3" from the rear of the pocket I set the bracket into the pocket about 1/16" deeper than the edge of the pocket, so that in effect the rear of the bracket sits about 1/16" farther inboard than the front edge does. I hope that makes sense. I just set the toe-in by eye because I just needed it to get close enough to be able to drive it to the tire shop a few miles away for a professional alignment. How close did I get it? I nailed the camber on both sides, and nailed the caster on the drivers side. They didn't even touch that bracket. On the passengers side the caster was off by just a hair. The toe was off, but I figured it would be.
I hope this helps you get it close enough to get it to the shop for an alignment!