If you have the answers then why are you asking the questions? If this is just a poser(your words) then why are you worried about 10-15 lbs. Yes, that's about the most you could possibly save in weight reduction. Besides, by mixing aluminum with steel bolts you will get a dissimilar metal corrosion. I would be far more worried about that then cracking on a street poser.
If you ask the question you should be prepared to accept the answer. If you are not then do not ask the question. You have gotten responses from 3 lift kit manufacturers. Not to mention some who have built there own lifts and rigs.
So far, genius, the only one who has answered any thing relating to my question is OZified. I wanted to know if anyone has experienced any cracking with aluminum tubing. NOT that YOUR SYSTEM is the best! Also, unless you were to grind the mill scale off both the bolts and the aluminum, you wouldnt have any problems with "dissimalar metal corrosion". My question is not if a solid cast aluminum lift kit would weigh as much as a steel tubing kit, it is about cracking of aluminum tubing. We all know that 50 lbs of steel tubing and 50 lbs of cast aluminum blocks are going to weigh somewhere in the same neighborhood. SARCASM. IF there is no problem with stress cracking of aluminum tubing, then I believe I can make a FAR lighter kit than what is offered, also for a fraction of the price. However, I did want to investigate knowledgeable peoples experiences to see if they had had any problems with ALUMINUM TUBING. As I figured this would be a wise thing to do before beginning my project. Thank you for your time.