One more thing to include in your planning/cost est (always happens!!), if you do the triangulated 4 bar, if you can't weld well the setup and welding costs are not a small item, and then you'll need to have the axle housing straightened as they will warp from the bracket welding unless it's done in a jig. With the leaf springs you may find a bolt in housing, if you work at it a bit, that won't require that extra step.