really people? the wheels are probably double drilled. 6x5.5 is the exact same as 6x139.7 which is what all full size gm vehicles run. 6x135 is ford bolt pattern. so it will work with both applications.
regardless, you will have some serious rubbing with only a 5" lift on a NNBS. i've got the same wheels/tires on my nbs tahoe with my 6" rcd set at 7" and i had to do a good bit of trimming.
This is what my buddy sent me