What the best torsion bar and leaf spring combo?

I have a 73 dart that was a slant six car that I used a V8 K member to install a 340 with a 4 speed. The rear end is a Dana 60 out of a B body and I want to know what size of torsion bars should I use and springs to get the best handling. Its has stock slant six bars now and stock V8 springs in the back and it handles like crap.