Automatic gearbox - thoughts/durability

Hi all,

Looking for some info on the mk1 auto box as to power handling and durability. I hear mixed tales, also tales that if a few tweeks/decent fluid is used it can stand up well.

Is the 4 speed box lock up on all 4 gears so once rolling torque converter slip is eliminated? I hear a lot of lock up clutch failures, anyone know if some eg v6 versions have a better lock up clutch?

I'd like some feedback from anyone with one, I'm thinking of a diesel app with higher power so handling a lot of torque. Anyone know if the box internals are much different for different models and if a LSD can be fitted?

Greg.