Yes I believe if you get past like 78 or something they were locked up...
I pulled apart a 68 and it had less clutches and smaller accumulators then the 76 that I ended up using..
Yes something like that my 77 is not but my 85 is. My 75 was not. I'm not sure about the lockup being good for performance or not but I know they are harder to find converters for.
