I was under the impression the .454 Casull Magnum was introduced in 1972. I have an issue of Guns & Ammo which has it featured in a gun test. Quite impressive at 2000 fps and 2100 ft/lbs of energy as I recall (I'm not going to go down into my basement to did up the magazine for this). And yes, it was more powerful than the .44 Magnum by a good margin. It used a tri-plex load behind a 300gr bullet as memory serves.
I think your right SB.
The 44 Mag isn't the awesome powerhouse it's made out to be. It really isn't much more powerful than the 30/30 which is considered minimum for Deer in many circles.
It is a very versatile cartridge though.
The Casull is more powerful and you can shoot 45lc in it. I love the 45 but accuracy falls off in the Casull chamber though.