HELP, rear end sagging bad trying to get ready for drag week

You need to decide if you want to control the axle with the leaf spring or the shock. I would replace the broken leaf and see what the ride height is. A flat spring not a bad thing if you have the shock for it. Crank up the compression for the street part and set it for the race part. Find a couple of spare leaves if you need them. I would buy a good quality double adjustable rear shock. I like to control the axle with the shocks, much easier to tune than with the leaves. I don’t like pinion snubbers. With an A body the front spring section is so short we don’t really wheel hop unless you have BIG power and STICKY tire.