This is a pair of #3919840 Rectangle port heads for a 427/435 hp motor. Used on corvettes with the L71 427/435hp option. Camaro and chevelles with the solid lifter motor 375hp designation. They are dated D-2-8 (April 2, 1968) and D-1-8 (April 1, 1968). a match pair that would be good for a May, June, or July Corvette, Camaro, chevelle. Cleaned and Magnafluxed for cracks. Been sitting on the shelf a couple of years. No cracks, ready to be rebuilt.