I have a 1985 Dodge truck with a slant six. It has a sticker on the valve cover with #'s on it and wondering what it means? Also will need to replace the gasket and is rubber the best one? Anything else need to have/do when i do this? Will do a tune up also. Thanks

Engine assembly part number. Used on the production line starting in the '80s to make sure the right engine configuration (emissions equipment, etc) went into the right vehicle.
Yes, but they're getting scarce. See this thread.
Tune-up parts and technique suggestions in this post.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.