You could also still safely drop a couple psi in those slicks. If 15 isn't working, try 14 and a half, then 14. Yours shouldn't need much less than that.
I PROMISE YOU that you can make what you have work without spending another dime on suspension stuff. Just a little tinkering with a few things.
Now, once you get it to hook consistently, you will start having to make upgrades as you go. But like I've stated in other post in this thread, these cars can be made to work with little effort. Hell they already have a 4 link suspension under them......
83 Olds Cutlass
85 Olds Cutlass
71 442. W-30