Composite Leaf's & rear shackles

I'm building a 65 Cuda for Time Attack (solo 1), it will be ran on road courses on the front I'm sticking with torsion bar(1.09"), with tubular upper A arms and 2" drop spindles. On the back I'm sticking with leaf springs, 1st I was thinking of going with composite leafs, anyone with experience with these? 2nd what's the best rear shackle setup, Should I build in adjustable height for setting up at different tracks?