I've got a 70 b body with p/n 454 & 455 s/s springs. I want to lower the rear about
1 1/2 inches. I'm already using the upper front hole in the hanger. I was gonna pop a couple leafs out, but don't know how many & which ones. Any input? If I can't keep enough rate I'll buy new ones, but wanna try this first.

try some lowering blocks. they're simple to install, may require longer u-bolts, and aren't expensive.

Yeah, I already have a pair in, but ever since i installed them the car rides like a tank. I wanna keep my ride height the same without the blocks.

I know this is not your question, but why should your car ride like a tank just from adding lowering blocks? It shouldn't, and adding larger lowering blocks should get the lowering you are after.

Is something amiss, like are the shackles resting on the frame?

No clue why it rode so rough after I put them in. Makes zero sense. I like the height with them in, I wanna keep that ride height, just lose the blocks. I'm just gonna take the springs to a local shop and tell them what I'm trying to accomplish. They do good work.

with that lowered ride hieght are your shocks bottoming out?? Just a thought.

shock plates should still be at same hight, most likly rearend hitting frame snubber or pinion snubber bottom out, you can take leafs out but you wont have super stock springs anymore

Nothing was bottoming out, the ride felt like the shocks were replaced with solid ones. That's the only way I can think of to describe it. Bumpstops are really just auxiliary springs, if I was hitting those it wouldn't feel solid like it did.