Why bother messing with a swiss cheese unibody if that is the plan. Break out the chromoly, chop saw n mig and just throw down on a full tube chassis. Dice out the firewall and floorpans with a plasma cutter and give it a suit of pinto . aluminum footboxes firewall and floors are a lot more straight forward than trying to not fold up a modified stocker. You never mentioned rear suspension and there is a whole lot more to hooking it up than weight bias. Incidentally this opens up some nice options. get a rear irs conversion kit for a factory 5 cobra. it comes with the cradle, narrowed control arms and cv shafts. add your own center section and bearing hubs. put pickup points on your chassis and bolt in a complete irs subassembly. Sticking with the giant girder and leafs, build a set of custom caltracks to fit. this is probably one of the most effective things you can do to the back of a leaf spring car. Guys can hook ,get consistent 60's and run 8's on a set of caltracks.