Are the Stall Converters interchangeable from E/A/B Series ?

I assume you mean torque converters?

No. I believe its -

EA to ED are the same.

EF to AU are same (however late ED's did get the ED style).

B series are different again.

The difference is in the size of the T/C neck that connects to the oil pump drive. They progressively got smaller to reduce pumping efforts.

6 to 8 differ

Thanks for the info