With all the great surplus rifles out there, you really don't have to settle for less.
It is true that some of you can't find .303 locally. But I bet that you can find some type of 8mm locally, and probably 7.62x54 as well. Almost certainly 7.62x39.
The Mosin Nagant, Mauser, and SKS are well proven weapons. You can get them really cheap as far as guns go (especially the Mosin Nagants).
If all else fails, pick up a couple 30-30's and call it a day. I can't imagine that there is anywhere in the US that you can't get a couple boxes of 30-30 ammo.
I guess what it comes right down to is that there is no one rifle that fits all sizes. Gotta look at your situation and see what works well for you.
I also brought up the idea of rechambering an Enfield on another board. It is a cool idea, but someone pointed out to me that I would be back to the same problem after the supply of 7.62x54 dries up.
I guess no matter what, you gotta buy what you want and stockpile a good supply of ammo and reloading components. I plan to keep my grandkids shooting my guns.