Detailed sources on modern heavyweights' training or nutritional regimens?

This is very accurate RD I think a lot of guys made room for a fad or a marketing gimmick Lou Nova and his “Cosmic Punch”?
I’d say (I’m guessing mostly) that old timers like a Ray Robinson got into good shape but they fought so often they stayed in shape.
Contrary to popular classic opinion I think the average camp would probably be reactively “pedestrian” compared to todays routines there would be no sprint ladders to near puking on the track, horsing big weights around, pylometrics and circuit routines simply “enough” - weight control, work for the wind, sparring to stay sharp that was all that was required and they were better fighters for it.
Ray and them weren’t getting back into shape all the time like they do so often now - they were maintaining they kept the engine warm so to speak lol.