Iceonly ,
Did ready lift verify that you bought the correct kit for your truck?
Gm has used 3 different upper control arms on these trucks.
The reason i would think it is the wrong kit would be the tire size change is neglible.
Obviously this a design issue as you replaced the a arm.
The good news here is that you should be able to leave those spacers in there and just change back to the factory arm and have no more issue.
All the new a arm does is change the ball joint angle. So that the ball joint doesnt wear out quickly.
My previous generation gmc ran a 2 inch level with significantly larger duratracs o er 60k with no issue on factory a arms.
My currenty truck had a two inch level for 1 year and no runs a 5 inch lift for the past 5 years . No ball joint issue. Factory control arms.