Most any race car can race in Super Touring and/or Performace Touring.
If your Alfa is really lightweight, and makes enough power to get close to 12:1 Lbs/HP (rear wheel), or better, then Super Touring fits, if it's less than Performance Touring is where you should be. Both set of rules are on this page: https://www.nasaproracing.com/rules
. Your car does not have a classification line in the P.T. rules, and if you are going that direction, you'll have to email Greg - the national PT/SD director. Let us know if you get stuck.