"I don't want anything bigger than my 404J and no shotguns or rimfires."
OK, sticking with your parameters of nothing bigger than a 404 Jeffrey and no shotguns or rimfires, here are my thoughts. First, a few personal notes about what I've taken.
On my first safari, I took a .458 win mag, a .300 win mag and a .270. It was a 24 day safari with lots of DG included. Those calibers worked splendidly, though I could easily have left one of the two light rifles home. When I had problems with my .458, I borrowed a .375 to shoot my 2nd buffalo.
On my second safari, I took a .470 NE double and a .338 win mag. I was primarily hunting DG and that was a great battery. I took a couple buffalo and bull elephant with the double, and used the .338 for a few other animals (though a 250 grain nosler partition did make a mess of a nice klipspringer)
3rd safari, a .416 hoffman and the .338 again. For a 24 day safari, again with multiple buffalo and both cats, that was a great battery. I also took a 12 gauge, which I shot more than anything else.
Last safari, a short SA hunt. I only took a .270 and it was fine.
OK, now staying within your limits, here is what I'd suggest.
Your .404 Jeffrey for dangerous game, .375 H&H or .338 win mag. as an all around medium rifle, .270 or .30-06 for light rifle. Chances are, you'll shoot 2/3 of everything you kill with the smallest caliber. The .270, .30-06 and .375 are all readily available calibers in most areas where you'll hunt, and that is a legitimate consideration. You should also be able to find .338 ammo in a fair number of places.
In this day and age, it is rare to actually need to take 3 rifles, and is enough of a hassle that 2 seems like plenty. In the future, I imagine that I'll only take my .416 and a light rifle, either my .338, .30-06 or .270, depending on what I'm hunting. There really is nothing I'd hesitate to shoot with a .338, though it is not legal for some dangerous game in many locations. If I were taking only 1 rifle, it'd be either a .338 or .375 in all liklihood.
You said no shotguns or rimfires, but you really should have those in camp in many locations. A lot of fun can be had with shotguns and rimfires. I've shot hundreds of rounds of shotgun and rimfire ammunition in Africa, and had a blast doing it.
