Please ID these cars- for ACADEMIA!

One of my son's friends sister is trying to date this photograph while doing some archival work. Please let me know what you think and I'll relay it back to her.

Is the one on the left a late 60s Plymouth Grenada? 

One looks to be a Caprice (left), maybe both. 

74 Caprice coupe

78 Caprice sedan

Brett_Murphy (Agent of Chaos) said:

Is the one on the left a late 60s Plymouth Grenada? 

'74 Caprice.  Round headlights, so pre-75, but without the goofy '73 rear bumper.

One on the right is a Delta 88 from sometime in the 80s.  Maybe 98?

Looking at the trim, hubcaps and what I can see of the tail light, I think the car in front is a 73 or 74 low end Oldsmobile. Same body as the Caprice. 
 

I can't tell exactly what model is, but the second car looks to be about a 78 GM of some sort, maybe also an Olds. 

Grill on the beige car looks taller than a Chevy unit. Might be a Pontiac or Oldsmobile.

Dark GM 2 door is 1974-1976 (my guess 1974)

Light GM 4 door is 1977-1979 (my guess 1977 and is clearly an Oldsmobile)

So, as for assigning a date to the photo, it could not have been before 1977.  Technically, not before Sept 1976 because Sept was when GM would launch the new year models.  

Thanks everybody!

New Oldsmobiles are in early this year.

In reply to wheelsmithy (Joe-with-an-L) :

But that was for 1980...

John Welsh said:

Dark GM 2 door is 1974-1976 (my guess 1974)

Light GM 4 door is 1977-1979 (my guess 1977 and is clearly an Oldsmobile)

So, as for assigning a date to the photo, it could not have been before 1977.  Technically, not before Sept 1976 because Sept was when GM would launch the new year models.  

Yep, I think John called it correctly. Both GM. 2 door is likely a Caprice/Impala. 4 door is an Oldsmobile, possibly a Delta 88. Both mid to late 70's. 

JWTFMFW

the low-trim nature of the dark car says Impala to me. My buddy's got a 76 Impala coupe that was his dad's last new car.