Sam -
If you dig through the old "Archery" (NFAA) Magazines, in the Pre-Pope and Young Club Days... you will find the annual listing of the NFAA Big Game Awards, which lists a lot of great information such as the bow weights used to take the animals...
All of Fred's listings that I noticed had 70# for the bow weight.
Fred used the best bow for him that was available at the time of each hunt from the 1930s to the 1980s... these are some bows he used to kill big game animals with in the 1960s... This information is from the poster shown. On some of the bows in the poster, the hand written dates and animals are visible on the tape on the bow...
Top to bottom...
1959 Kodiak purple heart sight window… in 1960 Fred took the world record Alaskan Brown Bear with this bow and it in 1961 Fred took a Grizzly in British Columbia with it.
1965/66 Kodiak white glass… in 1966 Fred took his Polar Bear with this bow.
1965 Exp T/D… in 1965 Fred took his Cape Buffalo and African Lion with this bow.
1964 Kodiak… in 1964 Fred took his bull elephant with this bow.
1963 Kodiak Dogleg… in 1963 Fred took his Indian Tiger with this bow.
Keep in mind there are several conflicting dates in Bear documentation about Fred's Hunts and the animals taken. Probably typos or someone not remembering a year before or after...