Dude, bolt-on notches are really shady, if you ask me.
Think about it: You're cutting away a peice of your frame..YOUR FRAME...and BOLTing on a plate.
If you're gonna notch it, I would HIGHLY suggest just going with a full-boxed notch. You can get one from Alter Images for about $100. It's worth it. Otherwise, you'll ride around everyday wondering if your frame is going to snap.
Why do you need a notch? I have the DJM kit on my 2001 and I removed the bumpstops in the rear and have never bottomed out. If you haven't removed your bumpstops yet try that first or at least replace them with smaller ones.
I installed a 4" block in the back and still had problems bottoming out. I completely removed my bump stops and added in two strips of rubber, as per Miniac's suggestion. It worked great, but the rear STILL bottomed out.
I just got my truck back from being step notch'ed TONIGHT..6" notch and boy is it SWEET. I'll be posting photos and stuff tomorrow. It'll be in the Tech area on the site.