The list is vast, but the easiest ones are rounds based on the .308, .284 Win, 7X57 or 30-06, and there are a wealth of cartridges in that range.
If you are willing to open up the bolt, extractor, and do some possible magazene/feed rail work, you can use the 2.0-2.5" H&H case, ie 7, 300, 338, 458 and various wildcat mags, as well as some of the shortened 404 cased rounds.
If you want to puts lots o money into it, no reason a 500 Jeffrey couldn't be built, as it is designed for the std M98 action.
If you are willing to do extensive modifictions to the action and magazene, a 375 H&H length round can be fit, but there really is no reason to do this with the CZ-550 on the market, that is set up out of the box, and you'd be lucky to get a std mauser into that shape for twice the price, or more.
Now, if you have a gunsmith do all the work to bring the action up to modern standards, ie for scope use, you will be able to buy a new CZ-550 action for less $, or a complete Ruger, Rem Win rifle.
I built a 35 whelen ackley on one, but the action for $75, and doing all the work but chambering, which cost me $35 from a friend of a friend, and free bases/rings, it cost me ~$350 to make a rifle out of it, not including the scope!
I am now in the process of putting a wood stock on, and iron sights, which will add another ~$200 to the cost, and the pre-inletted stock was given to me.
When it is finished, and provided I do a decent job, I'll have a rifle that would cost me ~$2000 to have built for me, though it would have saved me many, many hours of labor.
I can think of few better ways to learn the gunmaking art then converting a military mauser to a sporter.
If you farm the work out as an attempt to get a rifle for less cost then a factory gun, you'll have less rifle, and not be happy. If you are looking for the basis of a classic custom rifle, then figure exactly what you want in a custom rifle, add it up, have a convulsion or two, but forge ahead and get a nice gun.