My .02c
I would have waited to weld the perches to the axle untill after you get a driveline installed. Just install the rear without welding the perches so you can adjust pinion angle as needed, no shims needed. If you do use shims make sure you buy STEEL, the alum ones will crack in time and spit out leaving your Ubolts hella loose (this happend to me and luckly I cought it and only suffered bent spring perches)
I would get new drivelines ~ HighAngle or TomWoods or local driveline shop that can build some beef for you with the correct yokes/u-joints.
To measure your driveline = Xfercase yoke to pumkin yoke (the half circle area were the Ujoint seats into) that in your installed length. The driveline must be able to move inward and outward when flexing.
I have never been a fan of droping the tranny/xfer case mounts, at only 6in of lift you should not have to do that, I wouldn't.
I use CV-joints on both my front and rear drivelines. With CV type you point the diff pumpkin straight to the xfer case. With non-CV driveline you have to make sure Xfercase yoke angle and pumkin yoke angle are the same so they cancel eachother out when spinning (within 3deg I think).
You can also run a flange at your xfer case the eliminates the u-joint type yoke, 4bolts instead...
This is a 1350CV type with flange mounting at the Xfer .120 wall tube. & 1410 Ujoint at the rear diff. from High Angle Drivline.
Hope this helps!
Good Luck