273 Intake Manifold Question!

Do you know if the heads on your 273 are 64/65 or 66 and up??? The Edelbrock dual plane (ancestor of the LD340) is the D4B for 64/65 heads and, as mentioned before, the LD4B is for the 66 and up version. Both were originally designed for the 273 as the LA318 and 340 hadn't even come out then.