I agree about the durability of the old TH400 trannies from GM.  While I 
never intentionally slamed my '68 Firebird 400 ci Conv. into gear, I would leave 
the trannie in Low (read 1st), grab hold, hit the pedal, and once the tires 
grabbed, take off.  When I reached about 57-60mph the turbo 400 Auto would 
shift to S (read 'super' or 2nd) and leave about 10 to 15 foot of double 
stripped rubber on the ground.  Most everyone I knew at the time was quite 
impressed with 'peeling' out at 60 MPH.  The trannie held up just fine.
Motor mounts would last about a year until I tied the motor down with large
chains.  Oh yea,FYI:    Pontiac 400 ci bored 0.04 over   
                        Large Valve heads
                        Holley 650 Spread bore
                        Crain 'BLAZER' cam (don't remember the specs)
                        PosiTrac, Hooker headers, Dual exhaust
                        Get this (Conv., leather seats, power windows
                                  power top, AC, Cruise etc.) 

  Oh yea, I also pulled the 'Cocktail shakers' (weights) from the front
  and removed the lead pellet from the accelerator pedal. (Damn US regulations)   
 OH, HOW I MISS THAT CAR!!! 
  -- 0-60 under 6.7 sec  and about 6 to 14 mpg (well I don't miss the mpg)
  -- front wheels 4" off the ground with three quick jabs at the pedal.
  -- bent pushrods, stripped rocker studs,  every 6-12 months 
     ( I really wonder what kind of rev's I was turning - no tach)
Re: Improvements in Automatic Transmissions
  Anyone seen one of these lately?  I'd buy it back in a sec!!!