Go radius arms and chevy 56's in the rear and you will have more then enough flex and for a fraction of the cost. Also radius arms act as a sway bar thus helping streetability since you know damn will thats where this thing will spend most of its time.

The parallel 4-link has crappy ground clearance and cost a **** load, also no need for coilovers, get a set of deaver coils and bilstien shocks and you will be amazed. As for the rear 4-link, I think and you know as well you are getting way in over your head, just do a 2.5in chevy leaf spring swap that you can build your own pack and it will flex more then you can imagine, just add a traction bar. But most of all, remember its not all about flex and what you read on the web, stay inside your means and most of all your fabrication abilities and save yourself a huge headache and risk trashing your baby, ask me how I know..