Does this kit contain everything needed to rebuild water pump?
It is an impeller kit, so it is a repair kit mainly for the impeller. You may want to do a search for a complete water pump kit. However, the main component in any water pump assembly that needs repair/service is the impeller, so this may work for your purposes.
Looking for a water pump kit for a 1976 120 horse Chrysler engine?
We would need to know the original part number of the kit. You could consider contacting a mechanic or Mercury to get that and we could cross reference it for you if you call the number at the top of your screen.