Actually, there were three sizes of push rods used in big blocks. 3/8, 5/16 and 7/16. I believe the 5/16 was stock for 1972. 1967 did use 3/8 rods so if the guide plates are correct for those heads, you should be okay with 3/8 rods. But hey, if you have to buy new rods anyway, maybe the 7/16...