How do I get the lift I need without shackles?

you can use booster shocks, you can easily get those from summit, however they do wear out fast . But they will give the rear a boost. Other than that there used to be places that would re- arch your springs to the desired height. I have not had the need in many many years so no idea if anyone still does that. Have you tried espo again to see if they can give you more rake. Another thing to consider the ss springs are very stiff. I put those on the back of a 64 dart 4 speed car once and I would ( at least I am sure that's what it looked like) fly up in the air on every bump. I would feel every bump in the road, Had to change those out as I could not take it anymore. I then took them and put them on a 65 barracuda and it seemed to be less bumpier on that car but it is diffidently a more firm ride for sure.