You also mentioned the Guldstrand upper control arm modification that was popular for the early Camaros. This was done to help compensate for the short Camaro (and Chevelle) spindle by relocating the upper control-arm mounting (pivot) point lower. You don't need to do that when using the Global West tubular upper arms with the taller spindles. One thing you might consider is improving the front suspension's anti-dive. In my experience, the stock Chevelle performs very poorly in this area. Even with 900-pound-per-inch front springs, the nose still takes a serious dive under hard braking. If you look at the front upper control-arm mounting points on a C4 Corvette from the side view, you'll notice that the front mounting point is significantly higher than the rear mounting point. Effectively, the upper control arm points up at the front. This is one way to create what is called anti-dive. If you have an understanding of rear suspensions and how 100 percent anti-squat works, then this is a similar situation except under braking. We don't want to achieve more than 100 percent anti-dive because then the front suspension will rise under hard braking, and there are many reasons why this isn't a good idea. But improving upon the stock Chevelle's bad habits is a good thing. The trick is to not overachieve. I would suggest calling Global West and talking with Doug Norrdin about this, if you are serious about moving in this direction. He has developed a new product that will help with this, but I had to promise not to talk about it in print because Doug says he's tired of educating his competition. The solution is incredibly elegant and is bolt-on simple.
Now, we can move to the rear suspension. Of your options, I really like the three-link idea. The problem with the Chevelle's splayed upper control arm rear suspension is that the arms are very close together in the middle of the car. In the case of a left-hand turn, the left-side rear control arm front locating point pivots upward as the body rolls to the right. The right side front location point moves downward, but these arms are also twisting slightly, which in this case is good because it keeps them from binding. A typical aftermarket upper control arm is very rigid, and if the ride height has been lowered, these arms can easily bind. I bent two stock upper control arms in my '65 Chevelle during competition before Doug at Global discovered the car was too low and binding them under body roll. The arms would completely lock up under body roll, and then the rear axle would literally bounce off the pavement in the middle of the corner because the rear suspension effectively became completely solid. As the car was bouncing, it was imparting tremendous loads through those upper arms, which then collapsed. This twisted the housing in the car and shoved the rear tires up into the rear wheelwell—not a pleasant experience at 50 or 60 mph in the apex of a corner as you lose all control! I ended up in the weeds off the track both times.
Preventing this problem means eliminating the bind. Global offers a spherical bearing that installs in the upper mounting ears on the rear axle that effectively minimizes the bind, allowing you to use a tubular upper control arm in the rear. But an even better idea is a three-link that uses a single pivot point in the rear. Unfortunately, this also eliminates the centering effect of the splayed upper control arms that locate the body over the rear axle. That's why, as you've correctly stated, you need a Watts link—or a Panhard bar. The Watt's link is more complex, but offers tuning advantages over the Panhard bar. We could spend another page or two on that subject, but for the sake of brevity, we'll save that for a question from a different reader.
I have purposefully not talked about shocks because that is yet another area that could take an entire book to discuss. This may be a bold statement, but I think that if you have only money for one product (not counting tires and wheels), I would spend more money than you can afford on double-adjustable shocks. A high-quality shock absorber can do more to improve the handling of your car than almost any single other component. Of course, this means you must have a decent front suspension geometry that doesn't roll into positive camber under body roll. But once that is achieved, then the next most important thing you can do is spend money on the shocks. That's even true for a drag-race car. I don't think that quality shocks can be overemphasized. There is a plethora of shocks available for a Chevelle. I would again talk to Doug Norrdin at Global and all the intelligent folks out there racing their cars. I would talk with QA1, Ride Tech, Koni, and a newcomer company called JRi, run by Jeff Ryan, who put Penske in the shock-absorber business. The price can range from affordable to downright crazy expensive, but having experienced the tuning nuances of a high-quality Penske shock, it's worth the money if you want to go fast. Of course, then you have to learn how to tune your suspension in order to get the value out of this investment. If you just want to bolt on parts and then go out and have fun, don't bother with adjustable shocks. But if you are serious (and it sounds like you are), then double-adjustable shocks will pay off immediately once you learn how to tune them correctly. Unfortunately, shock tuning is an art form all its own that I don't pretend to fully comprehend. But even the basics will still get you 75 percent of the way there.
Lastly, tires are the overall key. With a sticky tire, a properly tuned suspension will allow you to negotiate any corner faster with more control and faster exit speeds. The tires are the final and ultimate contact patch between your car and the road, and all this suspension talk is just to be able to put more tire on the road for the entry to, the middle of, and the exit to the corner as fast as possible. Lighter wheels are better along with softer tread. Nearly all of the Pro Touring events now require 200 treadwear ratings on the tires. Also, pay attention to when the tire was built. I bought a set of tires once only to discover that three were dated with the current year, but the fourth was three years old, despite the fact that they all were “brand-new” tires. You can determine this by using the federally mandated date code required on all tires. The date code is the last four digits located in an oval box on the sidewall that will say something like "2613." That means the tire was built in the 26th week of 2013. If the tire was built on or before the year 2000, it will be a three-digit code like 269, which means the 26th week of 1999. There are an increasing number of road events now that require the competitor's tire be no more than three years old. If you only race a couple times a year, that can get expensive, but it's all in the name of safety. Have fun with your Chevelle—send us photos and an update.