Gear ratio and tire size 833 4 speed

The thing about tires is this;
>the tallest tire you can fit on your Duster is about 28 inches, and it sorta has to be inside the tub, cuz the outboard edge will be running pretty close to the bottom front corners of the quarters at the rockers..
> the shortest tire with decent width, is about 25.5 but that's already looking a little outta scale.
> so that gives you a range of 25.5 to 28, which is 28/25.5= about 10%, which just happens to be about the same percentage as swapping one gear size, in the range of 2.76s to 3.91s, except 3.73s which are in-betweeners. Once you get into the 4.xx series gears, the ratios spreads are closer to 5%.
> the bulk of tire sizes that you might consider for one of the large-tub performance cars like Dusters/Demons/ and Second-gen Barracudas, are gonna fall into a much narrower window. For example, and by the math;
a 325/50-15 is 28 ; these fit, but it ain't easy.
a 295/50-15 is 26.6 ; these fit right in and look right at home, but you will need to offset the springs, and get custom offset wheels, or get your rearend narrowed.
a 275/60-15 is 28; these look great too, and are adequate for straight-line work, and are a bolt-in
a 275/50-15 is 25.8; height-wise, these are already looking a lil outta scale
I see no good reason to run anything smaller with 275hp or more, nor would I ever run 14s on the back; but;
AFAIK there are no 265s in 15s
a 255/60-15 is 27; again looking good, height-wise.
So then, the window is about 27 to 28, which is 3.7%.. At 65mph, this amounts to 2.4mph, which, IMO, is not worth fiddling with; just install whatever tire that you like the look of and think will do the job, and let the cruise rpm be what it will be..

and one more thing when selecting tires; for straightline work, height is better than width. What I mean is, when faced with a contact patch limitation of say ~100 square inches; it is better to have a patch that is 8 inches wide and 12.5 inches long, than the other way around.

But if you drive like I do, slip-sliding around as many corners as I think I can get away with, a lil extra width comes in handy. When I come in too hot and I run out of steering correction, with the tires spinning, I just put a lil toe on the clutch, and when she is sliding sideways, when the patch stops spinning, it acts like a full-lock brake, and bam! she stops sliding. The only down-side is that I gotta know where my front wheels are pointing, or I might have a new problem, lol. So then, 295s are my only choice.