[HO455]

You are correct I am using factory upper control arms. To do so all depends on how low you want to go. The lowered ride height (not aired out) is the important part.
After I modified the lower control arms, did the caster modification to the lower control arm shaft, and installed all the new components I reassembled the front end I put the truck up on the alignment rack and started playing with the alignment. As I am bagged I decided on a ride height on all four corners and tried to bring the alignment in to the specifications I wanted. After several attempts and slightly raising the ride height in the front I was able to get a satisfactory alignment. I used some thick washers to replace some of the shims. There are plenty of threads for the nuts to secure the upper control arm and the amount of shims on top of the washers I made is acceptable.
The other benefit that I didn't realize at the time but it came to light not long afterwards is I have very little bump steer. If I were to lower the front end ride height another 1 inch (or more) and lower the bump stops correspondingly I would experience bump steer. And the upper control arm shaft bolts would be then be too short.
I don't have an actual measurement of how much my Burban has been dropped as it was bagged when I got it. (It was worn out and hacked to boot so it was a bit of a white knuckle experience crossing railroad tracks. ) But it looks like this at ride height. (See gratuitous photo of truck at picturesque highway view point )
And if funds don't allow upper control arms now. You can do what I did for now and later on when conditions are right install some different uppers and go lower. But when/if you do just have a plan for dealing with bump steer and your truck will be a joy to drive.

Disclosure time: I did have fairly unlimited access to an alignment rack to do this. Which was nice but I could have done it in my driveway with a couple hundred dollars worth of tools. There are videos on the interweb explaining how to do the alignment yourself with low buck tools. At the very least you need to find a shop that deals with race cars and understands what is going on not just what the book/ computer says. Or find a local racer (roundy round, rally, auto crosser or road racer) with the tools who wants to earn some cash helping align the truck.