My dog eat rat poison and it has been two months would it be too late to take him to the vet?

Anything we, or dogs eat is metabolized in a few days at most. Depending on how big your dog is and how much it ate there may be no problems going forward to some problems that may need mitigating only a vet could feel you. However, if the dog is still alive it won't die from the poison at this point. Depending on the poison though there may be lasting effects like I said, and it might bit hurt to schedule a physical to be safe just in case there are lingering effects.

Yes it would be to late...next time take him to the emergency as soon as possible

I I would say yes but I am not a Dr.