BBC / trans question '71 Malibu

[BobKnake]

After MANY set backs in life, I'm getting ready to start my Chevelle resto...

Need some light shed for me, since I've always been a Ford guy and I'm not overly versed in GM.
What my plan is as of now... Drop my 396/402 in my 71 Malibu.. It's going to basically stock.
I was originally planning on a 4spd (which I have), but due to increasing left knee issues, I've decided to go with an automatic.
My question is.... Turbo400 or Turbo350? My car is originally 350/350 - but long gone. Honestly, I would consider an o.d. tranny too, but it doesn't really matter to me, at least not at this point. Can't say putting a bbc in is really going to be a huge benefit in mpg's....



Also, Will my stock trans mount work?


Sorry for the stupid question... but I need to get a plan going. Really hate back tracking.