I've done a couple of C notches, My '99 R/T and my '99 Ram.
I wasn't a HUGE fan of the notch offered for the Ram, it's a trapazoid as opposed to a round notch.
When installing, I used a 3/4" hole saw to make the 'corners' and connected them with a sawzall. Worked great, just don't leave a 'square' corner to avoid the stress point. I had to clean it up a bit with a grinder (I'm kind of OCD) but once it was installed, you'd be hard pressed to notice it wasn't stock.
In regards to the 4 link, there is a lot more than just welding on a universal kit. Parallel links are the 'simplest' but they don't give ya the greatest benefit. With coil-overs I'm guessing you're planning on just getting a set height and calling it good, so a panard bar will 'work' just fine for you.
You might look into a Watt's Link instead, it keeps the diff centered over the entire range of suspension travel (Gen II Durango's use one stock, it's not some strange voodoo).
Sport Truck magazine a long time ago had a really in depth article about non parallel links, bar lengths etc. It was a pretty neat article, might try googling it.