tire options left in 14 inch ?

I want to say something in a non-critical way; so please don't take offense;
Since even a teener will blow through just about anything on a 14 x 8; why are you considering these for your 408? If you cannot fit wides in the wells, tall will accomplish more. So if you can fit 28s in there instead of 25s, that would be the way to go. Working the formula backwards; I see that 28s on 14s would be; 235/75-14s on 6.5s are 27.9 and 255/70-14 on 7.0s are 28 tall.
The tall narrow tire will put a similar sized patch on the road to a low fat tire, but the patch is in the direction of travel, and grows rapidly when airing down, which I imagine would be very beneficial to a 408.
Of course these tire sizes can be translated to 15s too. And IMO big and littles is very cool. IIRC the 70 AARs and TAs were big and littles;right on the showroom floor.
To fit a 28s on 15s would be;
235/70-15 on [email protected] tall, or 245/70-15 on [email protected], or 255/65-15 on 6.75s @28.05, or 265/60-15s on [email protected], or 275/60-15s on 7.6s @28.0. All rim sizes are the 70%-checking rims and according to the literature could be plus/minus 1 inch. I recommend rounding up to the next closest 1inch,at least.
I realize that there are no factory 15s in sbp, so you might as well spring for new wheels. And when you do that you can maximize your rim width and center them in the tubs. Wheel Vintiques will sell you a primered rally wheel in almost any combination you like, for almost dirt cheap.

I ran 275/60-15s, on 8.5s, for a couple of years, on the stock rear end in my 68 Barracuda. The aluminum slot-mags mightabin 4.5 bs. On the 8.5s I was able to run pressures from 24 to 30 on the street. The first summer BFGs or Coopers do pretty good. But once you burn them down to something like 70 tread left, then it seems you get into a harder base compound,and a lot of traction disappears. They stop squealing too. And then they won't smoke up anymore either. So they tell you when they're done, loud and clear.