I understand wanting to keep the factory frame rails and not building a complete back half. Also would suggest notching the frame in the spot that you earlier stated. The main reason i say this is because of the approach angle at full bump. With the front suspension and rear suspension at full bump, you want to look at the whole chassis to see what angle the frame rails sit. Me personally i like to have somewhere between 7-10 degrees, so that the front of the chassis is higher than the rear. From my experience this helps with the vehicle not wanting to rotate forward in a hard g-out or bottoming out all the way. Now, yes shock tuning and spring rates are a big part of controlling the vehicle and how it acts. To get down to the nitty gritty the chassis and geometry are the root of how the vehicle works. Keep in mind your center of gravity, the instant center, squat/ anti-squat, and of coarse the approach angle. Hope this helps once again just my 2 cents trying to help out. I have learned over time that there is no incorrect why of setting up your 4 link, all depends what you plan to do with it and how you want the vehicle to act.