I have to go with bucket on this one , properly installed rear lift blocks ,(as long as they are not to tall) , are fine. I have had many 4x4 lifted square's over the years and 90% of them had lift blocks in the rear.My 77 crew cab is not a wheeler , (mall queen) , but it has a hog block putting out 478 hp with blocks in the rear and 44 inch rubber and I love doing burnouts in it all the time,(people **** seeing big rubber get loose), with no problems. My 77 stepside with a 425 hp smallblock and 38's had rear blocks and it was beat through , mud bogs , deep snow , (I live at 6,000 feet), sand mountain in nevada , its hole life with out one block problem. When I first put it together it had a wheel hop problem , so I shimmed the pinion down 2 degree's and the hop was gone.
My son and I are building a 84 blazer for rock crawling right now and it came with 8 inch lift springs in the rear , we are throwing those in the trash and going with a shackle flip and a flat spring with blocks in the rear , (works way better all around than a high arc spring and no blocks) , so he can clear 40 inch mtz's.
So all the years and all the lifted square's I have had , (stout power , big rubber , bashing them off road) , never one rear block failure. Also in the 70's and 80's and now , fords and dodge's had blocks from the factory and I am sure some dude's beat the crap out of them off road and put hot motors in them with out block failure.
So for me I would take a small rear block and a flatter spring for a sweet ride and more flex than no blocks and a add a leaf or a higher arc spring for a worse ride and less flex.
