The 429 Cobra Jet/Super Cobra Jet block is a unique casting with “CJ” cast into the lifter valley with four-bolt mains down under. JGM Performance Engineering has studded these main caps with ARP studs for rigidity and security. ▲You should see a D0VE-A or D1VE-AA casting number in addition to “CJ” in a Cobra Jet block. Just the D0VE-A or D1VE-AA alone does not guarantee a Cobra Jet block. Pull the oil pan and intake manifold to ascertain four-bolt mains and “CJ” casting mark.