I am a 727 man. I'd destroy 904's with Horse power. Just think how long a 904 would last behind a 440 or a Hemi. Probably why they never offered any Big block 904's. If your lacking that much power to turn a 727 keep the 904 and rebuild it more often. Put a 7 1/4 in much lighter also.
Well you said it there, destroy with HP. What you really mean is torque. The General and Ford trans models 4Lxx and 4Rxx, the 60, 65, 70 and 75 is the design torque, X10.
When the General came out with the TH 200, it was designed for I6 and 305 2V engines. Functioned fairly well. Then some deranged einstein decided they could save weight in the Impala and Caprice models with a 350 4V engine. The torque ate them.
Then they added O/D. When they put that trans in the Grand Nationals they got beefed up. Then the hot rodders tinkered with the engines and the trans companies designed upgraded internals. They will now take 800 ft lb of torque, not cheap though.