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Discussion Starter #1 (Edited)
I am both elated and terrified to report that the SN95 Cobra springs DO, in fact, fit.

HOWEVER!!!!!! Its not a pleasant sight.



I'd like to confirm the speculation and previous research performed by those that have come before. (Click here for reference.)
-The rear springs have similar dimensions to the stock MN12 springs. The rears are a direct bolt in replacement, though as mentioned, thunderbirds use a progressive rate spring and the Cobra does not.
-The fronts won't even be close. They're shorter, wider and even if they did fit their spring rate will be far too high for MN12's coilover placement. While they do "bolt in" to the struts, and still fit into the spring isolators, albeit are slightly smaller in outer diameter, they are considerably shorter than the stock MN12 springs. In fact, when using the wall mounted spring compressor at work to swap them, hardly any compression was needed to install the top hat nut.

While I do not have pictures currently, (i forgot my phone at home today :/ ) I can safely say the front of the car is easily 4 inches lower than stock and the rear is either stock height or slightly higher. As reference, the front fender is about half inch higher than the tire tread. With this information, I don't believe it unreasonable to use Cobra fronts and an adjustable rear coilover setup designed for a Cobra (since the shocks are bolt in) to even the height, though custom spring rates may be advised. Heck, as is, this could be a cheap suspension alternative for someone trying to get into drag racing.

I will make sure to take pictures when I head into work tomorrow, but it looks silly without fancy wheels and tires...which may be the next step for this bird, not sure...
 

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Discussion Starter #2
Updated OP with pictures.
 

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Discussion Starter #4
So having driven the car for a few days now, I've found a few quirks with this setup.

Supporting mods and work done in addition to the cobra springs"
-17x9" Cobra R style wheels
-Front tires 215/55R17 Michelin
-Rear Tires 235/65R17 Continental
-Adjusted Toe to -0.02deg front and ~0.08deg rear (as close to recommended spec by alignment machine as possible)
-Front Camber set to ~-1.5deg for tire clearance
-Rear Camber set to ~0.0deg
-Caster is not worth worrying about IMO with this much rake, so I let it be. Cannot recall the measurement

-It handles about how one would expect a car looking like this to handle. Front end tends to dart, producing a lack of confidence in high speed turns.
-The car has not bottomed out in normal conditions, though I've been making an effort to avoid potholes for the sake of my new power steering rack.
-With the stock 3.27 open diff and ~29" tires in the rear, acceleration has suffered (though that's probably good for keeping me out of trouble)
-Front end bounces just a bit, though some performance shocks up front should be able to handle the height and spring rate.
 

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From a handling standpoint, there is such a thing as being too low. At this ride height
- On flat ground, I'm sure the LCAs are aimed upwards instead of being parallel with the ground; this is going to cause all sorts of strange camber changes as the car moves up and down and changes while the car is steering (ackerman angle IIRC). This probably explains the dartiness.
- If the goal is to homebrew a cheapie setup (and $28 650lb-in QA1 springs are too spendy) or just be different, I suspect you can try to raise the ride height of the vehicle by raising the bottom spring perch. You could even stiffen the spring here by increasing the # of "dead coils" aka the coils which aren't doing anything because they are already compressed.

Oh, you could also cut the rear coils to lower the ride height so the tbird looks like less of a doorstop.
While the rears might be an option, I think there are plenty of options for front springs.

-g
 
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