its a LOT of work to fit a very poorly designed axle
if you want to make a sierra handle then 1 of the best things to do is change the rear axle(or mod it)
it its an expensive thing to mod it,
if your making an axle fit i realy think you'd be better making some other else fit instead
theres lots of other options for the same kinda money with better geometry
i'd look into it a bit more before you commited yourself to it
if you ask most tuners what the weak point on the sierra chassis/handling is
i'd bet most if not all would say the standard rear axle geometry