Show That Lowered A-body!
That's very interesting. I know he's doing a HemiDenny slammer K and assumed this is out of necessity. He's also got a 20" wheel but I suppose that does not change things so much but just means less tire sidewall. He also mentions needing to raise the inner fenders. I suspect you avoid that with smaller diameter tires? I'm thinking of running 18s.
It depends what his overall tire diameter is. My diameter of the 275/40/17 set-up I have on the front of my car right now for mock up is 25.75" The Minilite rims have 245/50/15 tires with only 24.5" diameter and gives me 24" from fender top to ground. But I run flat poly 1/2" tall LCA bumpstops or no bumpstop at all.
If it is real tall tire AND you want the car low, you will probably need the 2" dropped spindles. I'm guessing Johnparts' 20" rims have a tire with at least 26.25" diameter (225/35/20?). Johnparts?? Around that size you start being forced to run a dropped spindle.
I've been thinking I may need to spend some cash on TTI headers. Kinda hard on the budget.
I've read a lot of your suspension related posts and have learned from them. I just installed the Moog offset bushings per your diagrams so I owe you a thanks!
I guess your wheel offset requirement will differ on a Cuda?
The maximum backspace setting in the front should be the same for any 67-76 A-body running 73-76 disk spindles or F/M/J body disk spindles. And might only be slightly different for OE 67-72 4 piston brakes. This is because the suspension and frame side is the same for all 67-76 A-body. You may run into sway bar interference with high backspace rims with an original 67-72 wide style front sway bar.
Remember backspace doesn't care how wide the rim is. Backspace in the front gives you an idea of the clearance between the rim to the suspension pieces and clearance between the frame/innerfender and tire.
I have 5.6" backspace 17x8 rims with 275/40/17 tires on the front of my Barracuda right now. That tire is too wide for that rim. Should be a 17x9 rim. But that is what I had for mock up purposes. My top of the fender lips are rolled and the bottom front corner of the lip is bend in about 2". And you MUST run "flat roof" type upper ball joints.
You could run that much backspacing in the front of your Dart IF you run Hotchkis or Hellwig front sway bar that are more narrow or have bent arms respectively. But you will rub/smash on the stock bottom front fender lip. A 245/45/17 on that 17x8 with 5.6" backspacing rim would work on your Dart, but you need one of those sway bars and the bottom front fender lip bent in 2 inches.