I saw every game that Clements played. I simply don't recall his receivers like Casper constantly bailing him out. Clements was a damned good passer. Keep in mind that Notre Dame ran an entirely different passing scheme for Clements than what Notre Dame is running for Book. Clements did not have the many high percentage short passing routes that Book has called for him. A much higher percentage of Clements pass plays were downfield throws. Again, different offenses for Clements and Book.
I will say that Clements is the quarterback that Book most reminds me of. I think that Book could run the Clements offense very well, and I think Clements could run the current offense as well with no problem.