Another rookie question for the pros- visual transmission Identification

I'm going to check out a motor/transmission combo this weekend. The guy selling the parts doesn't know anything about them since they belonged to his father who recently passed away...

I suspect the transmission is a 727... but will I be able to tell by looking at it?

I have seen 727s kicking around my Pop's garage all my life but they had the big block case (belonging to his GTX)...so I'm sure they look different.

The 904 in my Dart hasn't been out of the car since it was on the assembly line so I've never had a good look at it for reference.

Thanks for any tips.
Mike