Would 2 right side mp xhd springs work well in a 3800lb with driver e-body along with stock front rear sway bar? Thinking 1.03 front bars also, has .920 now. 99% driver no track car. 408 4-speed, it needs better rear springs.

Why would you not use the complete XD set for your car, why mess with success?
Inertia created by the driveshaft and the rotational force on the left rear tire makes it need a different spring than the passenger side, Ma Mopar figured that out a long time ago

If I had a set of originals that might work. This is not a drag car, its a driver. The new mp set has the left spring with 1-1/2" more arch than the right, the original b-body set of xhd springs I have has about 1/2" more arch on the passenger side. Just standing on the 2 new springs tells me no way the car will be level. Maybe this set is made wrong. I have heard you could use 2 rights to solve this, and works well on a driver. I also dont like the fact that the second leaf on right side extends all the way up under the eye bolt, but the left side is about 3" back....seems odd, on the b-body set, both second leaves support under the eye, the reason they do not wheel hop at reasonable power levels. I need the stock height of the 340 spring, with a stronger front section. I had heard of a-body guys using 2 right side super stock springs, just wondering what others have tried and what bars would work well since the rear spring rate will be higher, I assume the front rate should increase a little too.

Why not just add a blade to your current setup to up the springrate?

you can always adjust slight rear height differences with the opposite corner T-bar.

This mp set has a 135# per inch spring rate, at least that is what spring shop measured, afraid adding a leaf would make the stock 120# too stiff, always seems to be a disaster. Just seems weird that the left has almost 2"
more arch than the right. I read somewhere that 2 right sides is the way to fly somewhere, e-berg maybe? I would buy hotchkis but have heard the rear would be too low. Just looking for opinions from those that have used them. No way I try 2 springs with 2" differant arch.

Yes, you can use two right hand springs or two left hand springs or any combination you want. The spring rate between the two sides should not be different despite the difference in control ratio (leaf orientation) and camber(arch). I have never noticed any differences in left/right camber in XHD sets in any of them I've installed previously but it has been a while, I have to admit. SS springs, absolutely have seen radical left to right differences. XHD, not so much. FWIW, the left side is supporting a driver so they may have a slight difference in arch while the right side has to support torque, hence the leaf arrangement. FWIW, the E body set is splayed with the front eyes being narrower, whereas a B body set is parallel. No doubt this impacts both their leaf layout as well as their roll steer characteristics which is why they are not a duplicate of the B body design.

It used to be when you bought XHD sets, they came as a set. Only SS springs where sold separate. Looking at Mancini Racing, its appears you can now buy XHD springs separately. If you prefer to run two rights for a mirror image set up, then do it. Any shortcoming you may get from not using the matched set may not even be noticeable on a dedicated street car. IMO, 2" isn't much when you have a 3800# car plus potentially a couple hundred pounds of a driver and a couple hundred pounds of fuel. Plus, as mentioned, you can offset any imbalance in rear height with the opposing t-bar adjustment.

If you are happy with the feel and height of the stock 340 springs at 120# but need more control in the front segment, try adding a partial leaf on TOP of the main leaf from as far under the spring eye as you can get it to right up to the mounting saddle. This will both give additional support from upward, acceleration loading as well as downward, decceleration loading.

I definitely need more front strength, starts to wheelhop with sticky tires, and power is going up, ride is fine. My only concern was the right having 5-1/2" of arch, and the left having 7-3/8", the rate measured the same, maybe it will not matter. I am used to xhd being within about 1/2".

If you have the XHDs, you can always install and see what the results look like. How different is the leaf count and orientation from your originals?

For inexpensive experiments, you can add clamps to the front section to try and stiffen it up. Next step would be to add another half leaf on the top in addition to the clamps. If the hop is severe enough, a snubber with different height bumpers may need to be added.

Or disassemble your pack and customize leaf count and orientation to create a front bias while maintain rear segment layout and count.

In my experience, the XHD springs are a good match up to about the 1" t-bar range and larger than stock front s-bars. With stock s-bars front and rear, it might be a bit tail happy. This coul dbe okay depending on personal preference. Easy fix to this would be a 1.125 front s-bar.

Regardless, in almost in every situation, you want the front leaf at rest, straight, and near level, best first to have a good reason to divert from that.
A shorter front segment (A body) with same rating will be effectively better at controlling wrap up then a longer segment.

I have the xhd springs, just doing some research and think something else might be better, car is a little tail happy now, wheel hop was not bad, but starting, and riding around with the snubber 1" from the floor pan sucks. I am moving the springs in 1" per side also. I am thinking maybe the stock springs with the second leaf out of 2 right side xhd, clamped, and dearched to get height down, if the rate does not go up, in any case the xhd set will need dearched to get them at 1"arch in the car.

Have you upgraded the TB's yet?

If not, I suggest that first, then see how the rear likes that change.

Honestly, I've never read a "good" review of the MP springs. Most say they sag in a short amount of time. Some even say the main leaf starts to bend back the opposite way. I think there are better options out there for a higher HP car that will see some abuse. I have a set on my Challenger Rallye but its a very low HP car that won't ever "test" the springs. Even on my car the back end sits pretty low and feels soft. Granted I just have cheap Monroe shocks and Polyglas tires which might account for the "feel".

No changes yet going to be a winter project. Items I am changing.

K-frame to reinforced one
Lower control arm plates, has the better bigblock arms
Adjustable struts
Upper arms for caster not sure what brand not rod end style
Has firm feel box and 11/16 tie rods, quick ratio will not clear headers, has welded subframe connectors with 2 driveshaft loops.
Front sway to 1-1/4
1.00-1.03 bars
Rear springs, and b-body width housing maybe rear swaybar
The motor either a 408 or a 6.4 crate
Mount the whole mess by the pinchwelds, square the rearend, square the k-frame, equal distance the lower ball joints to the rearend, then align it. These changes should make it feel a lot better at speed.

I see complaints on all brands of rear springs, I like the design of the hotchkis, are they really that bad? I know the rate is a claimed 160, is that too stiff for this planned front setup? Was thinking soft rate is better. Sounds like I may be changing springs a few times so wanted some input from others experience, to get a close starting point.