Shocks: looking for Blistein quality at KYB price.
i had to block quote you down because you covered so much ground here. but let me start off by saying that some of what you're saying is counter intuitive to what you're thinking or what end goals you're trying to achieve.
I'm the first to agree that the '64 Dart, like every 1964 car that isn't a Porsche or a Ferrari, is sprung very softly.
But while I do want to tighten up the car's suspension just a bit (and I do understand that this is not a modern car – I have an E36 and an E46 BMW and have had 911s), I am not looking to turn this into a race car, or make it do improbable things, or drive it like I stole it (the slant-six makes it a poor getaway car, and no, I'm not going to turbocharge it).
I just want to be able to drive around the twisty roads where I live without feeling like I'm hurling it, and take a drive on the NYS Thruway without my knuckles getting white and without being rear-ended.
the stock slant six bars were the tiniest bars offered on factory show room cars, with only a smaller "drag race" bar offered by the parts department. upgrading these is absolutely essential. how big you want to go hinges on a few things: ride quality, type of shock you are willing to pay for, how much you want to pay for bars, end result.
.87 V8 bars are the absolute minimum i would run with a 6, with factory big block bars being next at .89 and if you can find them .920 bars being my 1st choice. all of these can be run with off the shelf shocks. from there .990+ bars really require a better shock such as the bilstein or QA1, etx.
specifically because you're trying kinda sorta retain originality, not have a buck board ride, do this on a budget, and you're not running big sticky tires, and you have a front sway bar, i'd err toward the smaller side of bars with .920's where you can get away with stock shocks if you want, or buy bilstein's and really compliment them. though i understand that the 1.03's are more available and afforable.
And I am trying, strange as that may sound on a board full of hot-rodders, to keep it as original as possible.
this is perfectly acceptable direction to take. i build a lot of cars like this. mildly updated suspension, bone stock appearance. better brakes, better spring rates, better bushings, better shocks, sway bars, slightly bigger tires. all the small upgrades add up to a nice riding and handling package. it's not gonna smoke an autocross circuit, but it'll be comfortable to drive and safe in modern traffic.
As I say, if I want to zip around, I can drive my 330, and I know I will never get a '64 Dart to compete with that.
au contraire pierre... you can indeed make an old *** mopar handle like a E46. here's the hotchkis taxi besting a bmw in a tire rack shoot out-- with the same driver laying down laps a full second faster than the ringer test car.
somewhere, footage exists of me in my 64 dart out hustling some E46's at buttonwillow on a track day. so, yes, it can be done. i have no doubt that the duster built by @72bluNblu would absolutely embarrass all but the top tier of modern performance handling cars, and that's all "old school" t-bar suspension.
And I really don't want to go changing torsion bars. And then adding a leaf to the rear springs. And then adding disc brakes. And then...
you've mentioned that you have a 911 (waves hi! i have an 80) and the E46 (which i owned one as well) so you know what a performance car handles like and how it rides. with the dart because of where you're starting at, you can tailor it to where you want to be-- wanna go point and shoot 911 or taut and responsive like the 330? easy to achieve.
but like those cars it's about system and about balance. big bars and a sway bar with weak *** saggy rear springs will just make it push. big burly rear springs and a rear bar will make it tail happy.
i wouldn't screw around trying to "add a leaf" or anything. i'd just buy springs that have the rate that compliments the front bars.
so, either you build out with the goal in mind from your designed system, or you make your decisions to "get there" with maybe doing the front first and then the rear as money provides. but just throwing parts because "that's what everybody is running" is a great way to wind up with something that rides like **** and handles like two wet cats in a burlap sack.
So, to be clear, if any of the tiny group that's reading this thinks that the Bilsteins will suck, or otherwise not be worth the $350 price differential on a Dart with an otherwise stock suspension, please let me know. I had planned to use them, couldn't find them, bought KYBs instead as a "next-best" option, and now, thanks to this thread and to Beams, I know I can get Bilsteins as I had originally intended.
So, if my original idea of using Bilsteins seems dumb to you, please tell me, and I'l save my money. If they'll be good, but (as always) "could be better if only I ...," that's okay, I'm looking for "good," and may do "better" somewhere down the line.
the bilsteins will not suck. they are 100% worth the money. even if you're running small bars, the difference in ride is noticeable and, if in the future you want to upgrade you can do so confidently without having to upgrade again.
remember, if you're building on a budget everything is a compromise. more money is usually good money, and good money usually only spends once-- the whole buy once, cry once philosophy.