1977 904 horsepower limits?

Plumcrazyreindeer said

Not a loaded question. I’ve ran them behind my mud rail trucks making in the 500 600 hp range bone stock. Yes the better parts put together by a good tranny makes them last a bit longer but that 904 makes more power to the ground than a light weight 727 is why we preferred them over the 727 in the slower classes

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While I agree with you there's no rocket science to how much horsepower a 904 will likely hold with a fresh rebuild for a purpose-built car. BUT, predicting how much a 60,000 mile, 41 year old transmission, with unknown history not being a loaded question?
With that said in 1977 904 I would believe to be a better candidate for a purpose-built rebuild then maybe an older one? It's been my experience the very little I have rebuilding 904 that the later years where for lack of better terms beefier?