That is exactly what I used to lower mine. The spindles are definetly the way to go for lowering the front if you dont mind the extra cost of them.
For the beltech 4" drop hangers, are the rivets for the stock hangers drilled out and the new hangers bolted onto the frame? Have you had any problems with the hangers being bolted on if so? Also are they grade 8 bolts?
I actually got a killer deal on my spindles. Only paid $145 delivered to my door and they were still brand new!! Got them from a member on another forum that just wanted em gone.
As for the drop hangers. Yes you need to drill, torch or grind the rivets out. I torched the heads off then used an air chisel to seperate the old hanger from the frame since it was still stuck on pretty good. The new hangers just get bolted on. I've had no problems with them being bolted at all so far but it's only been in there for one summer. I just used the bolts that came with the kit but I believe they were grade 8's.
I swapped the hanger with the box still on the truck but I will say if you can take the box off the truck it would make things much easier!!