You want streetablity? Why not just put some fiberglass leafs on it and be done with it. Weld a bar from inside of the top of the frame rail side to side and move your shocks in. That will give you a little more tire clearance without cutting up the car for a tub system. We still run a leaf spring system on our circle track cars and the old steel leafs can still be made to work with a little monkeying. Take a "NEW" set of steel leafs and slide the second leaf forward until the front of it is in line with the main leaf's eye. Re-drill the centerpin and take the third leaf and fourth leafs and turn them around. Paint all of the leafs with a graphite empregnated paint and clamp up the front of the leaf springs. You can use a square U-bolt shaped clamp for the rear but do not close it shut. This only helps hold the leafs in place. You will be shocked at how much traction this deal will make and still give you a nice ride.
We build this type of leaf spring for the street stock oval track racers all the time. I've got these all over the USA and it's a winner!!! It's cheap and fast. Or just bolt on some fiberglass leafs and be done with it.