Ive had a leaf added at the spring shop to many of my past vehicles. new mgmt. came in and price skyrocketed. to a point that I can buy new from ESPO and a couple of other outfits but it used to work fine.
On my 78 Sport Fury I took the springs in and had them rearch them "only" and it was great for the remainder of that years "cruisin' season" but I think flatter than they originally were, now.This car has 54k original miles, it had about 8k less on it when I had them done.

I have seen on some of the Jeep forums where guys build their own "basta$d pack" to add height and strangely their most common "donor" set of leafs is 87-96 Dakota or another "like" Jeep to what they are working on. What this is, is a mixture of leaves from the original application (have to use original main leaf from "your" application) and mix/ match leaves from the 2 sets to get what you want. and usually wind up with 1-2 leaves more than stock.

I have bought the "add a leaves" before, and they aren't as "application specific: as theyd like you to believe, width of leaves is most important. I used a pair listed in their guide as being for some Ford, when I did my 94 Dakota 6-7 years ago, did myself in the days before I had my own 2 post lift.

Strange this comes up as I just did what we are talking about on the back of my 96 318 Club cab 4wd Dakota last Sunday. had 3 leaves plus the super thick bottom one, was sitting a bit low in back... my donor spring pack was a 70s up to 93 D/W series truck. My son had stripped a Cummins truck (hed gotten it engine-less) and sold much of it in pieces, but one of the reasons that he got the truck carcass in the 1st place was for its nearly new rear springs..... the PO had recently had them replaced. Problem was my kid drives a flatbed, and though ol' Dad told him to strap them down, he didn't.... and lost 1 of those new springs.... so he bought another new set for his '90 from (I think it was) ESPO. I kept the 1 remaining new spring around, and about 3 months ago I stopped by the spring shop and got new U bolts, new spring clamps, and new center bolts wanting to do this "eventually".... well "eventually" came Sunday.
It didn't take long and was MUCH easier on a lift with a screw strand than with 2 sets of jack stands, and a floor jack rolling around on concrete....
Right under the main leaf this particular spring pack had 2 leaves the same length. and were nearly perfect length to go spring eye to spring eye on the Dakota, and the center hole was pretty well spaced too. I did like the spring shop used to do when I had them do it, added 1 leaf to each side right under the main leaf, almost as long as it as well... these spring leaves came right up to the edge of the front eye and a couple inches short at the back.
I only had 1 problem. on the driver side (1st side I did this to) I stripped out my new center bolt, so I used the one intended for the other side. I used a grade 5, 3/8-fine thread bolt on the other side (its what I had) and strangely it fit the hole in the rear end perch better without grinding the points of the hex off like I thought I might have to do.

I wish I'd had some gr 8 bolts on hand but... 1) at the time I HAD to get this thing done for work on Monday and 2) the whole "working on it on a Sunday" thing went against me on finding fine thread grade 8s at the time. But I must say that as easily as the new center bolt that I had gotten from the spring shop stripped upon reassembly, I doubt it was a grade "anything".

You can cut down the main leaf to whatever length you need if youre gonna do this, not too bad in a metal cutting chop saw/ but if you think youre gonna drill this stuff forget about it. I ruined several bits trying to enlarge the holes in the ends of the leaf that had holes, for the new snap-in spring pads they gave me.... and more trying to drill the holes where they didn't exist, to install spring pads on the leaf for the other side. so I said "forget it". the truck has 211k on it already and at 70 miles/day, I don't think I will have it more than another year or so because the miles are piling on so fast.
So far big improvement in ride, will know for sure when I pull my camper 7 hours away next week. just a popup, but with all my gear and tools I take with me in the bed of the truck will be the real test. It does ride a bit stiffer. "but its a truck" now to do the same thing to the Fury. I see in various listings that those cars came with either 4, 5 or 6 leaves depends on how it was optioned. Mine only has 4.
The hardware for this job is all over Ebay and quite cheap. just takes a couple hours.