Diff spacer kits

[Cliff14Denali]

I see that some companies have diff spacers to help with the driveline angles due to a lift up front but was wondering if anyone sold just the spacer kits? I bought a spacer kit years ago when I lifted my 96 4Runner and it helped even with a small lift. My truck currently has the Bilstein 5100 up front with a 1" setting and a 1" spacer on the bottom of the shock. My axle angles and upper control arms don't look to be in the best angles for wear and tear longevity. I see that Rough Country sells the spacers with some of their lifts.

[ChevyTrucks_95]

I'm also interested in this. I have a 4" Tuff Country suspension lift but wasn't given a diff drop and the lower control arms aren't very flat.