Springs support the weight of the car, shocks are supposed to only have to control the motion of the car and settle it back to neutral. Don't ask shocks to support the weight of the car ... not what they are made for. Trucks have helper springs that can be added. I suppose the same could be done to a car, but would look pretty gruesome. Facelessnumber (Drew) did a nice tech article about adapting Econoline van lower springs to the Mav main leaf. That might be a future project here. You can try several combinations of leaves until you get what you want.
My car was a California car and half the shock crossmember is gone and there's a big dent in the trunk floor from an air shock.
wouldn't shackles be a great choice? they sell the 3.5" and 4" in the autokrafters catalog. the kits arent too pricey either.
Mines also a Kali car.. Light surface rust on a few spots inside where water settled, on the body where the paint is SUPER faded and along the rear end... Oh, and on the outside of All 4 drum brakes... Musta got lucky.. The air shocks on there have be low(psi) because I can easily bounce the rear of the car by hand. plus the air lines are hella old, an been passed away.. But I sure dont want to tear my beloved first classic apart.. So dont blame me for taking out the trash!..
Generally, the higher you pick the back end up on a car, especially a nose-heavy one like ours, the more it will handle like a bowling ball. If you want a raked stance, focus on dropping the front height.
By picking up the rear end, you take the positive caster out of your front spindles, which were more than likely aligned when the car was level and it will not handle well at all. Plus your headlights go way out of adjustment. Now pick up the rear end, then re-align it and re-aim the lights and it will be much better.
For cheap at autozone, you can add a 1-inch block at rear spring to lift the car a bit. Or stack 5 or 6 of them for LOTS of lift and most likely a very dangerous driving machine. I used the same blocks to actually lower my rear an inch. Picked up a little with 4-leaf springs, but not much, 1/4" or so. Bigger rims and bigger tires will lift your rear up. Just gotta watch the clearance in the wheel wells.
Just an FYI - if you ever had a chance to put your car up on 4 electronic scales and lifted the rear up, you would see that you are now transfering more weight to the front wheels making the rear lighter and the nose heavier. Lowering the rear rolls more weight back to the rear and that would help to plant your rear tires under load.
I really don't believe there is a substitute for a worn out spring but a new replacement; anything else is a bandaid at best. I beleive that for any type spring, automotive or otherwise.