Looking for expert help. I have a 12 bolt differential on a 1970 Camaro Z28 that I purchased in 1988 (original San Diego car). Am bringing car out of storage after 35 years. I just got around to looking at stamping on passenger side axle. The stamping is COZ 0302 G 2 with E below. So, the COZ is 3.73:1 and 0302 is March 2nd for 1970. G is Detroit Gear Axle and E would be for posi. However, the Z is stamped harder. Is that normal? Also, the E is below. Is this all legitimate or could someone have re-stamped the axle or changed axles. The car was built 1st week of April per cowl tag and build sheet. Also, are those welds on axle factory? I paid a very reasonable $500 for car in 1987 and it is real Z28 as I found two build sheets. However, the gears in the differential are not 3.73:1. Looks like highway gears were installed by prior owner. The two build sheets were found under driver side back seat carpet and one above gas tank. Any expert help is appreciated.