Do I have to use them in matching pairs(right and left)? Or can I use 2 rights or 2 lefts? springs in question are P3690455 and P3690454. Also plan on using arengineering adjustable hangers.

You can use them in any combo you desire, left and left, right and right, left/right does not matter

I use a matching pair but as said you can use them any way you like. They are supposed to be made to work best as the pair you buy but many dont like how the car sits with the pair on them as they usually sit uneven. But whenever I put a set on I just adjust the torsion bars to get the car sitting even. This is how my cars sits with a 3400 lb pair of SS springs on it. And yes I had to adjust the torsion bars to get it to sit level. Ron

i keep going back and forth on whether i'm going to do the 3400 lb SS springs or if i want to do the XHD springs and add caltracs in the future...

67 coronet.

obvious difference is the front spring segment length.
maybe another difference is the spring rate.
not sure if i want the added height of the SS springs, it sits pretty low as is with the 5 leaf factory springs. another inch would be perfect.

When you adjusted the torsion bars to level the car with the SS springs, did you have to crank up a little more on the driver's side bar? I having a hard time figuring out how the torsion bar adjustment would be able to level the car side to side in the rear or are you talking about front to back leveling?

I had a 65 dart with 003/003 (came that way as a roller). when done it was level & the springs rode high and tight. I loved em

I don't know why the SS spring package needs to sit higher on the passenger side. Yes the spring is stronger but stronger does not need to have more arch. In coil spring terms you can have a stronger but shorter spring.

With that in mind I am going to dearch the passenger side spring so my car sits level. Not much else has changed, it will still have the stronger spring on the passenger side to combat axle lift.

I just bought two of the right side P3690454 for my car recently. I figured having the half leafs on both sides ain't gonna hurt.

Last time I bought a left and right side I got a severely mismatched set, they looked like they were made by two different companies. Those went back to Summit.

My Savoy has the 454,455 springs and it sits pretty level and I love the ride height

Initially the springs were designed around having a 100 lb battery (ballast) located in the passenger side trunk area, and the fact that the car torques over to the right and squats on the passenger side rear wheel in a full throttle leave on the light, once designed with these over compensating perimeters in place, they haven't changed in decades, plus the fact they were intended for drag use only

The car on launch torques to the RR, Uhh WHY???,
OK now why would they make that spring a bit stiffer? to control the chassis, Plant the tires equally, and send the car STRAIGHT forward.
In doing so, yes the RR will sit a bit higher. But if all else is RIGHT, front and rear suspension wise, The car will PLANT the tires equally and go STRAIGHT FORWARD. Trying to level the car for aesthetic reasons defeats the purpose of the design,

My Demon has the 3400# S/S springs and it sits level.

The extra height on the pass side was NOT to compensate for body torque.

It was to compensate for the weight of the battery that was supposed to be in the trunk on the pass side.

So, if you used the SS springs as engineered there would be no height issues.

But if you don't know what you are doing you will have issues and then blame others for them.

No blaming here just looking for some input. It will be more street than strip. Also they appear to be better quality than xhd pieces. Jegs has them for $126 shipped. Cant beat that.

OK, Sure, OK,

I believe the R/R was high so yes I cranked up on the drivers side and down on the pass side torsion bars. How much depends on how high one side is over the other side and yes I could get the car level doing it that way as I have done it many times. And I am talking side to side not front to rear as you have to change both bars the same when changing front to rear. Since mine is a street car I wanted it close to level. And my battery in my trunk is actually on my drivers side because I was running out of cash when I got to the battery in my trunk and my buddy gave me the extra cable he had. But it just would not reach to the pass side so I put my battery on the drivers side and its worked fine for me. Ron

I use 456 and 457 SS springs. It sits noticibly higher on the right rear despite the front end measurements being dead level. I never really realized how lopsided it was until recently when the Dana went in. It hooks really well on 275's, goes straight as an arrow and pulls the left front a little off the ground. My best 60 ft. is 1.59. I do still have the battery up front for convenience.

The right rear spring was not designed to compensate for the weight of the battery - was designed with a stronger rate and more leaves in the front segment for "bias" - to reduce the amount that the right side of the axle wants to "lift" off the ground.
The early Maxwedge cars had no battery in the trunk and they had this bias control already built in.

Torque reaction from the engine contributes to pulling the driver side front off the ground. The more you load the right rear the less driver side front lift you get. There are other forces in the rear that "pulls" the right rear axle "up". That is what the bias is trying to prevent. With ladders and four links and such - I believe you use the coil over to compensate for this - and/or by preloading the passenger side ladder and locating points - but I have no experience with those. Take a car that is level without the SS springs then add the SS springs - you are supposed to load the driver side torsion bar to level the car out - this "preloads" the right rear tire.

I run two passenger side 2800lbs springs on my 3700 lbs cars. The ride is firm, but very compliant on the open road. The best ride and overall performance on the rear suspension of any Mopar I've owned in the last 35 years. I do have 1" lowering blocks on the car to adjust the ride height to my liking.

In the past, I had used Caltracs & the stiffer 3400lbs SS springs and the car rode like a pick-up with both, and only hooked hard on very smooth surfaces.

Dr Diff suggested running the lighter SS springs, and the results are nothing short of amazing. I do run a set of properly adjusted slapper bars on the car. I know many folks regurgitate the story that they don't work on Mopars, but I know otherwise, as do all the local hotrodders & tuner folks and especially the guy in the Hellcat I beat in a drag race at Willow Springs last spring.

If you can't level the car out with the torsions, it's bending in half. If the front left is raised, the rear right has to go down, but not necessarily the same amount. The front right may come up a bit, too. Just play around with them a bit, and measure all sides to see what's changing.