60s 727s vs 70s 727s

So I'm trying to put a car together for a friend and I went to my transmission core pile and I see a lot of 66 to 70 dated cores along with a few 74 to 78 cores.

I'm thinking the latter ones are better to use and get parts for but I will admit, I don't know much about torqueflight.

So are there any advantages to either one. I believe they are ALL non lockup. I don't think I've ever had a lockup type before because 78 is the newest I've ever had.

Where's the automatic guys?