70s movie. A man and his clone are trying to find out who cloned him and why they are trying to kill them

In the mid-70s I saw a movie on TV (USA).

A man is working in a lab type facility (more computer or physics lab instead of medical lab) in a remote location. Something happens and his lab either burns or has an explosion. But he was able to escape the destruction, and eventually the facility, through a sewer(?) tunnel (It might have been an escape tunnel or exhaust steam tunnel).

When he exits the tunnel (1/2 mile from the facility?) he sees someone drive his car away. (I think he rages at the gate guard for letting someone take his car and either takes his security vehicle or another company vehicle to go home.)

He finally makes his way back to his house and finds his car there, and another man who looks just like him and acts just like him. His wife thinks the other man is him.

Eventually they decide one of them is the original and the other is a clone. But they don’t know how, as the are not working on cloning at the lab. I think they figure out who is the clone pretty quickly. (maybe based on last memories, or recent injuries that one has the other does not.

The rest of the movie they are trying to figure out why he was cloned, and by who, but they’re inquires causes whoever did the cloning, to realize he is not dead and they try to correct that mistake, to start hunting them down to kill them (The clone too since he knows to much.)

Same sort of situation as Arnold Schwarzenegger’s movie "The 6th Day"

I ‘think’ the end of the movie takes place in a abandoned or closed amusement park. (I seem to recall him climbing around on a old wooden roller coaster being chased by the killer. (The clone was dead by this point)

Eventually he kills whoever was trying to kill him, (Maybe the killer fell from the roller coaster or was hit by the coaster cars.)

So as the original is making his was out of there, the encounters the same man again (uninjured obviously a clone of the killer) who points a gun at him (We see gun barrel pointing at camera) says something like "What a waste" or "Such a waste" and shoots him.

End of movie.

Now I ‘think’ the reason there was clones of him (and others) was for weather control stations. Like 50 stations all over, each with the same clones of a few people running them.

I also ‘think’ the killer was his supervisor at the lab, (or at least someone he knew at the company/government running his lab. But I might be wrong about this one.)