I agree with Mitch, go big.

While what you listed are effects on the system, the impacts you suggest are implying that the suspension system is like a go kart and all things are the same, where in this case, they are not. We are discussing the lever arm of force that is being applied to the chassis under compression. If I were to solid mount the suspension system, it would cause the same issues and the force would be applied to the chassis instead of being absorbed by the suspension. By making the suspension too stiff for what it was engineered to withstand, you will accelerate the fatigue to a car that we all already know was not assembled to the highest of standards. And these failures aren't brand specific. Look at the fatigue issues that the Mustang guys have with their spring pockets. They figured it out quicker, and then even Mopar jumped on board with engine compartment bracing.

Hello,

With a better handling car the force will go up when used as intended. The forces will also occur at a greater acceleration/rate due to the added stiffness of the suspension. This will increase the fatigue rate along with the higher forces of the improved handling.

Damon

Interesting... Dan , where does an e-body fail first ?

In our experience, the three major fail points were:
-upper inner fender wells where they "attach" to the firewall
-Inner fender wells to shock tower
-Rear shock tower to frame horn

That was with 2 above average chassis'; about 30k street miles driven mostly in CA, AZ and NV; and probably 500 track miles and 2000ish autocross laps split between the two. Your results may vary.

So how do you properly reinforce these failure points?
I am currently getting a cage welded in and would like to address it while its still in the early stages

I've owned my Chally since 1975, always been rust free (stored winters), bought it with 22K odometer; been autocrossing it since 1975; car went through major transformation in mid-80s, including progressive changes in suspension (TBs, leafs, bushings, shocks, etc) primarily for concentrated hi-level SCCA Solo II/autocross competition, as well as for some hi-speed road course events). Streetable, but mostly trailerd between mid 80s through mid 2000s. Odometer currently has ~78K (put ~5K miles between mid 80s~early 2000). Chassis/unibody has no cracks or weld breakage, no stress cracks, etc... I know every inch of the car. Best mod ever for improved suspension handling was progressing stiffer with the TBs... the 1.24 is simply the largest to fit within the factory hex openings.... and a 1.24 TB is still very reasonable to drive daily... other mods compliment the "package" to my car.... again, primarily intended, and following the SCCA class rules for "E/Street Prepared".... rules have since changed a little since my past heavy involvement up to early 2000s, so a few other selective mods could be done, including welding in SFCs (must attach to the front and rear frame rails, not the leaf spring point).

The original T/A-AAR race cars used something like 1.4 diameter TBs.... makes the 1.24 and smaller TBs really weak by comparison. I had the opportunity to talk "unibody stiffness" with some Chrysler engineers face-to-face in the early 80s.. they told me our Mopars (concentrating on my E-body) had the strongest unibody designs compared against any makes, and even the AMC Javelins were very strong. At the time I was considering the "SCCA-Solo allowed Bolt-In SFCs"... they told me unless they were welded in, not to worry or bother with them (and I still don't have any SFCs.. maybe/probably someday). Our unibodies can certainly be strengthened, but I've never experienced any unibody or weld cracking, despite extreme g-forces (soft/ultra-sticky compound tires, such as Hoosiers). The car is intended to be driven at autocross and road course events, and certainly avoiding bad roads, pot holes, etc when driven on the street/hwy... If I were concerned about the ride stiffness, I wouldn't drive it on the street/hwy... even with the 1.24 TBs in it now, as well as some friends of mine with A-bodies having 1.14 (even 1.18), driving on the street/hwy is just fine and compliments the handling for better personal enjoyment.

Big TBs aren't for everyone, but small TBs (1.0~1.6~1.10) only lend the question: "These aren't bad at all... what would larger TBs be like?" That's why I encourage at least mid-range TBs like ~1.12-1.18 for best moderate results (leaning towards street/hwy as a larger % of someone's driving)... and still other mods are needed to compliment (leafs, shocks, etc). Don't forget.. "the nut-behind-the-wheel" will make the biggest difference.

Boy, been on Moparts over ten years, and finally discover we should be picking our TB sizes based on possible spot weld failures. Who knew?

I just purchased an AAR cuda that showed little to no rust only to find out that the inner frames have begun to rust in some locations. front drivers side at the rear K frame mount and outbored passenger side torsion bar spot. Im not worried about originality as I plan to drive the car and autox. Im bummed about the rust but repair there are many options now. Just glad I found it first before I through in bigger bars and such. I guess it gos to show these are old cars many people have handled them and you have to seriusly look them over and address the weakness of the car.

A-body frame rails appear to be weak even in factory stock state.