Newbie with a '69 400 firebird convertible. Had new leaf springs installed (4 leafs not 5 since it was a 400 convertible with A/C) The problem is, it still sits low in back and leans left at least 3/4" in the back end. The front suspension has always seemed to sit a little high for my liking too. I have been assured that the front suspension is correct and that leaf springs are correct. I have read that it was normal for these cars to squat a little in the back end. Can these cars twist over time causing the frame to bend some?
What options do I have to help level it out? Front Spring clamps? Spindle drop kits? Airshocks? Leafsprings pads? Extra leaf on the side that sags? Suggestions please!!

all birds sat a bit low in rear , looking like they point up in front....I lowered mine up front 1 inch (by cutting coil springs one full coil, the cheep way)....others have used lowering springs...

if it leans to one side in the back , it CAN be a bent subframe, sounds weird , but if its bent up some on right up front ,it pushes left rear down...and vice versa....you could fix the subframe or adjust front coil by inserting a spacer lifting opposing corner

both these are cheepie versions of 'how to', not the best way , but works.

I put four new springs into mine also...and my left rear sits a little low like yours. Front is perfectly level. I can say with 100% confidence that NOTHING is bent. We tram-gauge measured the heck outta every inch of this thing in the process of installing new frame rails, weld-in subframe connectors, solid body bushings, etc. The work was done with the car clamped firmly to a Car-o-liner frame jig...which means we not only x-measured and straight measured, but we also measured everything up & down off a perfect plane from every corner of this car...both with and without subframe installed and eventually welded permanently to the unibody. And my buddy who has straightened unibodys for a living for 25 years, and who has structurally rebuilt about 20 first gen F cars in his lifetime, assisted me with the whole thing, and without a doubt this car is now officially straighter than it was when it left the factory...I bet we spent 30 to 40 hours in measuring time alone over the course of this basket case project...

Yet it leans a little in the rear only. About 1/2" difference from wheelwell to ground. I blamed my new springs for being slightly off balance, but I'm not positive. I think the only way to confirm is to swap my rear springs left to right. Not real interested in the hassle...

And in this very recent topic, David Langley mentions his does the same, and Firebob says his does too, leaning slightly left in the rear EVEN AFTER HE SWAPPED HIS SPRINGS SIDE TO SIDE:
https://firstgenfirebird.org/forums/ubbthreads.php?ubb=showflat&Number=261630#Post261630

So I now count that at least FOUR of us, in this VERY small community, over the past few weeks, have mentioned our Birds sit a little lower in the left rear than the right rear? I find this all very interesting, and FAR too coincidental...

To answer your very original question, indeed factory setup these cars look like a boat taking off...rear low/front high. I didn't care for it and leveled mine out. My replacement rear springs were ordered in a heavier duty version, and they sit higher than stock and are VERY very stiff, which I like.

If you ONLY want to raise the rear a little bit from where it is now, and keep your springs, the easiest/cheapest/fastest alternatives for you are: 1. Longer shackles, or 2. Air shocks.

I have always wondered if the "lean" had something to do with the staggered shock set up. Would be interesting to see if the 67 guys experience the same thing.
Not sure if they still make them but aftermarket shackles with multiple height settings could be used to raise one side and then the excess material cut off the bottom. I wouldn't personally recommend air shocks.

I have replaced rear springs on one '67 and three '68's now. All came out level (within 1/4" side to side) on the first try. Maybe I just got lucky?

Generic shackles are still readily available:
http://www.summitracing.com/parts/mrg-1300

Gentlemen,thanks for the feedback. Anyone else with similar experiences or suggestions?

Mine leans a half as well to the left, I am using the original leafs rebuilt. From the sound of this thread I may as well leave it or try and shim it somehow, perhaps where the leaf bolts to the axle? Kind of hate walking up behind and seeing the lean!