318 block/340 heads?

1wild&crazyguy said
Some 318 heads have an X on them, so the X alone won't be the final say, pull the cover and look for a last 3 digits of 894/915

There are also some casting lines that are diff between 318/340/360 on the ends of the heads.

Thanks will check after work. I have another question in the attached pic there is a arrow pointing to a pluged vac port it had a short piece of vac hose that went no where. I plugged it. what the point of open vac hose Carb air fuel mix. Just wanting some input before I get home. What i plan to do is vac gauge the intake and adjust mix. and attempt setting timing,