Generally speaking, 6 lug is 1/2T and 8 lug is 3/4 or 1T on Chevy trucks, as is seen in TC's info. The 6 lug bolt pattern was used on Chevy trucks from about the 30's til now. Some years just on 4X4 and 5 lug on 2X. Cars had 6 lug also but not sure of BC. 6 on 5 1/2, in the metric era, is known as 6 on 139.7
