81 chevy lift

dude dont do it!!!! i have a 78 blazer with 4 inc rancho springs up front and a 4 inc block in the back......i really don't like the back set up...i really suggest against the block and add a leaf setup it will ride like crap and not articulate...you can just do the rear shacke flip with the stock leaf springs to get the 4 inc lift in the back..then up front get a 4 inc lift spring pack and steering correction and your done!! i would even take out the rear overload spring to give you a softer ride and better flex.....btw with my 4 inc lift im clearing 35s but i just trimmed a little in the front fenders.....  
Solid axle chevys can't be beat!
My dream truck: 73-91 chevy 3500 crew cab srw with dana 60/14bolt, 6 inc long travel lift with KING shocks, 37 inc tires and a 24v cummins diesel, nv5600 and np205

You are making a mistake there bud.  The first guy gave you the best advise.  Forget the ad-a-leaf.  Look for a good used set that is made for the rig and go with it.  

I just finished puttin a 4 in rough country suspension lift on my 86 k20 about 4 hours ago. I bought the lift off ebay for $360 shipped to my door and it came with everything, springs for the front, blocks for the rear, all new u bolts,all 4 shocks and boots, raised steering arm, and brake line relocation brackets. Me and 2 buddys started on it yesterday at 1 and finished this afternoon. I currently have 33's on it but they fit b4 the lift, i plan on puttin a 3 in body lift on it to put the 38's i have in basement on. with a 4 in lift you can fit 35's with light fender trimming.