Yea, wow, flashback. GRS1 used to be the only option back when I built mine...
IMO Go with t-case gears, leave the diffs alone. Lowering the diff gears will apply stress to the shafts, lowered t-case gears applys the stress mainly to the u-joints. Which would you rather carry spares and replace in the field? I had it down I could change a u-joint out in less than 10mins. However the stock shafts aren't the best and tend to warp at the u-joint ears. I ran 33's with a very healthy 1.3L and a GRS1, could hit 80mph on the highway easy. Even had to take a pic back in the day cause nobody beleived it. 78mph going uphill.