Perhaps I need to make a few clarifications. On 2 wheel drive GM trucks, they are 6 lug up to '70, with the 6 x 5.5 bolt pattern. '71-'98 1/2 ton 2wd are 5 x 5, '99-'12 are 6 x 5.5. On 4x4 1/2 tons, they are 6 x 5.5 for all years. For fitment to the '70 and older GM trucks, '87 4x4s are the cutoff, as the '88 and up use a deeper backspacing due to the change in suspension geometry.
