Toilets, Sinks, Showers, Tubs and Disposals - Cracked tank needs replacement

I need to either replace a toilet tank or, if need be, replace the entire toilet.
It is an American Standard 4049. The tank is cracked. I don't know the capacity but it is larger than replacements I have seen. I suppose this tank is no longer available unless I get one from salvage.
Is it possible or advisable to use a lesser capacity tank with this bowl? If so, how do I make sure I get one that will fit correctly?
Or should I just go ahead and replace the entire toilet?

You will waste more time looking for an exact replacement than it is worth. In addition, you should replace the entire toilet with one that has a 1.6 gallon per flush tank. These tanks are not retrofittable to your present bowl, so don't go getting any ideas. Replace the whole thing. You will be happier.

My only idea is to do it correctly. Otherwise, why would I ask for advice?
Thanks for your input.

You will be surprised how many times people want to cut it short and find out later they made a mistake by doing it. It was not meant to say you would do it, just an input for you to analyze.