Where are you people measuring at? My Challenger isn't particularly low, my buddies car is easily 1.5" lower... I'm running 235/60-15 tires (26.1" tall) and at the fender lip I measure 22.75....
That's why the factory never specified ride height by using the fenders, rockers, or other body locations.
That's a good point. It's an easier measurement to make but it is less accurate. There's also at least 1 model year of fenders that have a lower wheel opening, by about an inch. I forget which year and whether or not it was a full model year or whatever but there are Challenger fenders out there that have a lower wheel opening, so if your car has those your suspension clearance could be the same as mine despite the lower fender measurement.
On any car, the key point is the amount of available suspension travel. The shortcut to measuring that is just the distance from the bumpstop on the LCA to where it contacts the frame. To be practical your torsion bar has to allow about the same amount of travel as is available for the suspension to move. So, if you only have 1" from the bumpstop to the frame, you need to have torsion bars that are stiff enough to operate in that amount of space and no more, otherwise the car will be constantly hitting the bumpstops. Now, the travel at the wheel is different, based on rough geometry the travel at the bumpstop location is about 40% of the wheel travel, and of course the lower bumpstop to frame is only have of the full suspension travel, the other half is from the UCA to the upper bumpstop.
So, the important point is not how low the fender opening is, it's how much suspension travel is available. And since this is the internet, I would say that 1 Wild R/T would have to post a picture of his LCA to frame measurement. I have seen some really ridiculous ride heights posted with the claim that the car "rode fine" and the owner didn't have any problems, ie, it was a practical, streetable ride height. One car in particular that I'm referencing was an A-body that sat at 24" to the fender (note, this is different than an E-body for suspension and ground clearance). That owner claimed the car rode great and handled well. It was literally riding on the bumpstops. All the time. It had stock torsion bars, and the suspension was basically the rubber bumpstop. That's the internet for you.
With 1.12" torsion bars on my Challenger I occasionally bottom my suspension, and I have about 1" from the bumpstop to the frame. It's about the right ratio, the bottoming out is pretty infrequent so it doesn't effect "normal" driving. My bumpstops on that car are a little over a 1/2" tall, I run shorter ones on my Duster, so I could probably lower my Challenger down to 24.5", swap the bumpstops out and still be ok for suspension travel. But that would put the header flanges on my car less than 3.5" off the ground, and from past experience that's not a practical clearance for a daily driver. That's of course my opinion, and different headers have different measurements to the frame so they would differ on ground clearance to body measurements as well.
Sorry, I know it's not a E body but I run 24" to the fender opening with a 26.3" tire. The only practical way to do this is an aftermarket suspension that will pull the wheels in far enough to clear fenders when turning, I used a HDK front end (Hemi Denny K frame) and 2" Wilwood dropped spindles, I also raised the motor/Transmission 1" in the chassis and also raised the transmission tunnel and inner fenders 1.5" to provide proper suspension travel. It is a lot of work to do it correctly to avoid all the issues mentioned, there aren't any shortcuts to achieve the look and be street able.
The track width issue is manageable without custom suspension. With a 18" rim like you run the backspacing can increase until the wheel hits the frame, no fancy suspension required. Also keep in mind that on an E-body the backspace to maximize tire clearance is completely different than an A. B and E bodies can use 0 offset rims for close to maximum tire clearance, on an A-body with factory style suspension that number is +30mm. It's a whole different ball game. But even on an A-body the front tires you run are possible with the torsion bar suspension at the ride height you run. I run 275's on 18x9's, if I dropped down to 255's like yours I could lower my car substantially more with regard to fender clearance. My Duster sits at about 24 3/4" currently with 275's, and I use stock spindles and LCA's. When I swap to the QA1 tubular LCA's, which allow about an extra inch of suspension travel because of their lower profile, I could lower my car to your specs with the torsion bars. I don't think I'd like the UCA angles though, so drop spindles would probably be necessary, which would probably take a 19" rim for tie rod end clearance. Or a conversion to heim joints on the tie rods.
And second is the "street able" argument. This is an opinion, and it means different things to different people. Yes, your car can be driven on the street. In my opinion, coming from someone that has been daily driving A and E body mopars for the last 8 years, your car does not sit at a practical ride height. Sure, you can drive it to shows and the dairy queen, but if you drove it every day to the grocery store and had to deal with potholes and speed bumps every single day I would be that you wouldn't leave it at that ride height. You'd drag headers, you'd smash mufflers, you'd bottom things out that would concern you. All of those things happened to me when I was running similar ground clearances on my Challenger. Yes, that's my opinion, but after 60k miles in my Challenger and 10k in my Duster I would say it's at least an informed opinion.
Finally, you can run 2" drop spindles with the stock suspension and have the suspension travel issue handled, even at the ride height your talking about. I ran drop spindles for awhile too, before removing them because they weren't necessary to get to the ride height I felt I could practically run on the street and the suspension geometry is better without them. Yes, it takes planning to make it work with the stock style suspension but it's no different then how you had to plan your HDK suspension out methodically to achieve the results that you have. To be clear, you can't run the stock torsion bars and probably not the stock UCA's to do this, so when I say things like stock style suspension I mean the torsion bars are retained, not that they're factory stock.
Don't get me wrong, I LOVE your car. It's amazing. But not all of the results you achieved require the use of coilovers if the same thoughtful approach is applied to the torsion bar suspension. I know there are other reasons why coilovers were used on your car, but limiting the scope to just a suspension point of view you can achieve the same results with torsion bars if 2" drop spindles are used.
Wow, I learned something new today.... Turns out "The only practical way to do this is an aftermarket suspension that will pull the wheels in far enough to clear fenders when turning,".... I've put over 75K miles on my car & never had an issue... I drive fairly aggressively, I take my car on roads others don't want to go on for fear of damage.... But apparently it's all wrong... 
It's not all wrong. But I would like to see your LCA to frame clearance. What torsion bars are you running again? If I remember right they're pretty large...
