Would like to know the best way to install the shackle when mounting the leafspring/rear end to the car. Should the shackle be mounted to the spring or frame first? Would it be better to get spring in the position and install the shackle at that time? Should there be any lube used with standard rubber bushings? would :o

It doesn't really matter. You're going to install the shackle really loosely, so I have found it easiset to hang the shackle from the frame, and bring the spring to it. You just have everything finger tight until you put the weight back on it, so you don't bind anything.

I lubed the bejeezus out of mine with chassis grease to try and keep it from fusing to the metal pocket like the OE ones do. I thought about using anti-sieze, but wasn't sure if it might attack the rubber.

Hang the shackles first as already stated. Maybe use die electric grease to lube things up. Tighten everything up after the car is back on the ground and allow some time for everything to settle in place.