73 to 77 chevelles or monte suspension help SRINGS HELP!

I RUN at waterford speedbowl in ct. Its a 3/8 mile with decent banking . I run what we call super-x class and we have sricked limitations no mods to suspension except racing springs and camber +/- 8 . So my issue is ride hight to get my 73 chevelle low enough for good rear lower control arm angle for good traction, oh yeah cause we have to run street tires. Which im running 255/60/15 all around cUse they all have to be the same. So everyone i know runs g body they run 11,s in the front and single pigtail 11s inthe rear this wont work on my car tried spare springs from a buddy's car way to low and no travel up front. Im not sure if 12's are the answer im undecided what to do dont want to spend money on springs i cant use and on a major budget since sponsor dropped out . So im asking if anyone has a clue about what a good starting point would be and knows itll work .im not asking for secrets juat some good advise. It sucks cause i got good power and a good car just gotta get it to the ground. I greatly appretiate the help if anyone can thanks guys. JIMMYRACECAR aka Griz