17" Magnum 500's
Those of you in My age bracket, say maybe -10yrs & up(that's ~50+), will well remember all of the shocks being sold marketed as 'radial tuned' in the '70's '80's early '90's when bias-belted tires were still readily available....and still OE on A-bodies to the end of production. The larger Mopars got radial tires starting in '74 IIRC. The dampers make a difference, & it goes way beyond just a "good pair of shocks" or "stiffer" shocks, even just dual jounce/rebound adjustable types fall short. Take a modern even basic strut from a car & it is dual gas-charged to be 'neutral' at ride height, which makes them a real F'n sweetheart to change(or the coil) even with a Brannick compressor, all of the damping & tuning revolves around the weight/spring-rate/strut extension at rest...the avg. Mopar guy/gal is simply not going to get this by buying 1.03" bars, good bushings, & Bilstiens...as good as they are.
I'm blessed that a back injury 16yrs on(which was really a 'final straw' after multiple one's I could ignore), I have been able to manage, with fewer relapses now that I retired from wrenching Pro........but when I'm in the ShelbyZ & I see something I can't avoid coming impact-wise, I still grimace & hold on & pray it doesn't set it off, I still work it plenty...but carefully.
This is true to an extent, a modern car has more engineering going on than what you're going to achieve using 1.03" torsion bars, a good set of bushings and some Bilsteins. But even that combination is far ahead of what you'll get if you slap a set of 17" wheels on a car with factory torsion bars and KYB's.
The market for available suspension components has gotten MUCH larger with the pro-touring movement, and there is absolutely no reason why a Mopar with large diameter wheels has to ride worse than one with 14's. Maybe it won't be like pulling a brand new M series Beemer off the lot, but it can be a lot closer to that than you might think.
For example, I was running RCD Bilsteins on my Duster with 1.12" torsion bars and 275/35/18's. They're a good shock and the car rode well, but when I changed to Hotchkis Fox's the ride quality improved even more. The Hotchkis shocks were a better match to the combination of wheel rate and tire that I run, and I'm sure I haven't even found the
BEST shock for my combination yet. The factory would set the combination by looking at damping graphs and a mountain of suspension data, the rest of us have to do a little trial and error because even if we wanted to do the calculations not all the data for the shocks is published publicly.
The problem is the wrong-headed mindset that running larger diameter wheels MUST result in a harsher ride. It's simply not true if you use the appropriate components, and those components are available.
But the nice ride is from the suspension design and not from the taller sidewall on a 78 series tire.
It's a spring and a shock, like everything else. MacPherson strut style suspension was originally designed and patented in 1947, so like torsion bars, coil springs and even coil-overs etc it's really nothing new and was originally designed for use with tires that had very different capabilities.
If you use components that complement each other, you can have a nice ride. If you just slap some stuff together without respect to the actual capabilities of the components, you end up with poor performance/ride quality.
The suspension on these cars is actually quite good with regard to its geometry, especially if you lower the car (even slightly) and add positive caster. At that point then it's just a matter of maintaining your suspension travel and matching your shock to your wheel rate and choosing a good quality modern shock that was intended for use with larger diameter wheels/shorter sidewalls, of which there are now plenty.