dogdaddy - On your questions concerning the axle mounted above or below the springs, the deciding factor may be the desired ride height of your truck. The way they are mounted now gives you a higher overall rear stance, where switching the axle to above the springs will significantly reduce your rear ride height and possible remove sufficient axle motion in the process. Your choice depending on your goal.
On the use of those existing axle upper "ears", I would say no if you are sticking with the leaf spring set up. They will serve no useful purpose. Those were originally designed as the upper two points of a factory 4 link suspension system used in GM A and G-body passenger cars. Below is a screen grab of an original A-body rear suspension showing the 4 links and all that made that system work. I'm familiar with the design as it's what is currently residing under my other half's '66 Chevelle.
I'll let others catch up on your new info and offer their suggestions from here.
