That footage proves that boxing is ageless. Anyone can do it at any age. I'm 33 years old, and perhaps I'll start training for the ring tommarrow.
While two were at odds when Johnson became champion and skirted Jeanette, it was all water under the bridge for this W.W. II Bonds rally. Johnson was a selfish SOB out of the ring, but this is one time where he deserves a pardon for his past sins. Johnson did the sparring to raise money for the USA. If you put Frazier and Ali in the ring at 70 years of age, Frazier will try his best to get the KO.
If Muhammad Ali is still living at age 70 ( another 4 years ), he will likely have to face Frazier in a wheel chair.
Frazier is in bad shape these days, but he'd meet Ali again. Wheel chair boxing exists. I have seen the photos.
That footage was from Boxing's Best: Jack Johnson. I wonder if they have the whole program on youtube? Louis and Ali are there.