If I were buying the rifle strictly for use in Africa, I would go with a rifle chambered for the H&H. This is based on my experience in Africa (Zim) with missing ammo for an H&H and replacement ammo was located in no time flat. Replacement ammo for a 7mm Rem Mag was a different story as there was none to be found. This jives with JJ's statements that finding H&H ammo is relatively easy. I know other people have used the .375 Ruger successfully in Africa and a few rifles are surely floating around over there being used, but at this point in time and in the foreseeable future I don't think the ammo for it will be very commonly available. Thus my choice for the H&H.
In terms of rifles, I would personnally spend the money for a M70 Classic in .375 H&H and put my worries away. I would always pick the M70 over the CZ (too heavy for a .375 and I like the safety on the M70 better) and the Ruger (not chambered for what I want).
That's just my 2 cents. That all being said, if I were you and found one rifle fit me better or felt better in my hand over the others, I'd choose that one and not worry too much about weight, safety style or chambering and just go with it. Even if you choose the Ruger and loose your ammo, its a certainty that there will be another rifle in camp that you can borrow and in most instances, your ammo and/or rifle will show up in a few days so there really isn't a need to get too worried about it all. It does suck when you can't use the rifle that you've been planning on using and practicing with, but such is life and you'll deal with it just like hunters are continuously dealing with the unexpected everywhere they go.
Best of luck to you in what ever you choose.
