[jeepdaddy2000]

am looking for advice on the Preload amount for the Differential Side Bearings.

You are asking about the carrier bearing preload?
If so, start with shims on both sides since you have to move the carrier to set the picture depth.

2. Is it really just a crap shoot, i.e. put some in and your good?

Yes. Sorta. Not too loose so the carrier moves and the races spin, not too tight so the oil is squeezed out and the bearing runs hot. There is some leeway between these two criteria.

What thickness of Preload Shims should be used on a Dana 30? This is the additional Shim thickness above what it took to achieve zero endplay.

You can use as thick or thin (stack) of shim(s) as you need to get the preload you want. Traditionally, you will have a couple of thin shims on both sides to start with and shift them from side to side to set the picture. Once you have the R&P set, you can adjust the preload if needed (I usually set up my carrier with the preload already adjusted), then double check the picture. The adjustment always goes on the coast side of the carrier as adding to the load side can move the ring gear closer to the pinion.