You won't find many 0-4-0's in N-scale, but you can get 4-4-0's. Minimum 'normal' track radius is 9 3/4 inches, and just about everything will work on that except the extremely long stuff. Down to about 7 inches you'll be absolutely fine with most smaller stuff. Below that is possible, but you'll want to check with the actual engines you plan to use. I've seen 5.5" and apparently some have successfully used less. Try it and see before you glue it down! Many smaller engines have deliberately under-gauge wheelsets which will allow you to cheat on your curves, but may make tight switches a problem...
Charles
P.S. of course it will look bonkers, but I'm supposing you're not so worried about that