The backspace is too deep for use on the earlier trucks, especially on the 1/2 tons and even moreso on the Colorado. The bolt pattern on the '88 and up Silverado as well as the Colorado is the same as the earlier trucks. Up to '87 4x4 uses the same bolt pattern and backspace as the early trucks. 3/4 ton used a mix up to about '00, some have the deep backspace, some have the mid backspace (about 4"). The mid backspace wheels will work on the IFS trucks, might rub on a hard turn on the I beam trucks.