If you are interested, I have these springs collecting dust in the basement. Eaton Detroit Spring DS01, 4 leaf. 175# spring rate leaf springs, arched 1” taller than stock. Used one summer then changed direction and lowered my '68. These are stiff springs and are arched 1” taller than stock. $400 new. Condition: Like new. $75 + shipping. (Big & heavy. Will be expensive to ship)
Research and see if they will work for you.