If you are interested in racing a Porsche 944, there are a considerable number of cars prepared to Porsche 944 Cup / PCA SP2 specs which are very comparable to ITS (they are permitted to compete in the Fidelity Power Systems Pro IT ITS class). They are in line with the SOA to start with an existing race car. Cup cars do not seem to be fully competitive in ITS; I don't know what it would take to make them competitive.

Terry