u-bolt size for lift blocks

:confused2: I want to buy a set of lift blocks for my Yukon but all the kits I see say that the u-bolts are 3.25" apart on center the ones on my yukon look to be 3.75 or 4" apart what do ya'll think?

Where are you looking to find the U-Bolts? If you are looking at a local AutoZone the kit may be off. Check online and I'm sure you will be pleased with your selections