With the exception of a few one off builds (like mcreedys car) they are all national midgets. There's nothing "special" about them and all parts and engines transfer over. The main difference between the chili bowl and national classes is at the chili bowl they're permitted to run 10 in left rears and 12 in right rears whereas most national series limit size down to 8's and 10's.

That's the jist of it.