Several years ago before they went under, Super Stock and Drag Illustrated did a comparison. They took all the major autos and tested them bone stock. They spun them to 6K rpm and measured the HP it took to turn them. Remember, this is bone stock. Some of these show just a little improvement when modified (Powerglide), Others improve greatly. (Turbo 400)
Turbo 350 27 hp
C-4 29 hp
Turbo 400 39 hp
C-6 41 hp
They also had the Mopar trans, but I don't remember those.
Also weight wise I have weighed 3 of the above on my bathroom scales.
All were dry with no converter.
C-4, 164 tooth bell, 105 lbs (71 model)
C-6, small block, 147 lbs (85 model)
Powerglide, 92 lbs (72 model?)
Turbo 400 (with Ultra Bell added) 146 lbs. The Turbo 400 was reported by another guy in a similar thread on another board.
Actually the person that invented/perfected the fluid systems in todays modern automatic transmissions did his own testing. Other than weight there is really no gain to be made between automatic transmissions. They (3 speed) all have to change drum rotation & that's what robs(negligible) power. Physics says that once an object is in motion it tends to want to stay in motion. Once you have the rotating mass, it keeps going. Thrust bearings are the biggest power theif. As for bastardising a Ford to install a 'Glide, that's really not the transmission Ford put in one. If 2 forward speeds are so great... why do Pro Stocks have 5? I'm sure this will piss off the hybrid owners... bet you can't go as fast as my C-4 & it's 10 years old. She'll run mid 8's on a small shot of nitrous, runs low 1.20 60' times & I trans break the Hell out of it. Oh well, let the bitching begin!
I love the c4's, thought I just got through "bastardizing" my 75 maverick with a powerglide. I ran a c4 for years and still have one in my '74 maverick street car. There's nothing wrong with them, just in bracket racing, there is one less shift to contend with. Also, the first gear ratio in the 'glide is similar to the turbo 350's second gear, so therefore it's easier on the tires at the initial launch, and less tire spin in a "traction limited" car. Now that I've run a 'glide, I probably wont go back to the 3 speed in a bracket car..at least not anytime soon. It's way, way too easy to drive a 'glide equipped car.
Pro stock cars have a very narrow powerband, and therefore have to use a 5 speed to keep the revs in the band. Us bracket racers have our relatively low-revving wide powerband engines that seem to favor a 2, 3, or even 4 speed autos.