regarding the universal joint at the rear axle .
yes, that was a concern , after i had the longer shackles installed .
the angle that the u-joints had to travel in each rotation is greater .
in actual practice after 11 years that has not been a problem .
the rougher ride is the major downside .
i had a local 4WD modification shop do the change shortly after i bought my pickup new .
had i known before i spent my money , i would have chosen to alter the Front leaf spring brackets instead .
because i use a snug top canopy on my truck , my access to the bed is only over the tailgate .
in the stock height the bed access is higher than it needs to be for easy access .
i am not a fan of 1500 pickups ( for towing) , which are lower .
i am a fan of diesel pickups which are higher and rougher riding .
i have kept this diesel gmc 6 years longer than any of the 6 new pickups that preceded it .
if i ever decide to replace it , i will modify the front supports of the leaf springs to lower the pickup .