NOS OEM GM manifold stud nuts. GM part number 838780. 

All 19 nuts are included as shown.

These are all brass and measurements are 

• 3/8 - 16 x 3/8 inch thick.

No gm package- i found them in the jar in the old dealership parts department. These are the old / early issue that have no identifying markings.

These are correct for all Chevrolet cars and trucks 1929 thru 1982.

• Includes Corvette, Chevelle, Impala, Camaro, Nova, One-Fifty, Two-ten, BelAir, Etc.