Faith and Saving Faith by Gordon Clark (Jefferson, MD: The Trinity Foundation, 1983) is a weighty book well worth the effort it takes to chew, swallow, and digest its fare. [It is not an easy book to read.] In it Clark argues that saving faith is no different in kind than any other type of faith. The only thing which changes is the object of the faith. He thus rejects the distinction between head knowledge and heart knowledge. He also shows that there is no essential difference between believing in a person and believing that a certain proposition or concept is true.
If you read the book, be sure to pay special attention to the foreword. It is outstanding.
One disappointing note in closing: Clark fails to delineate exactly what proposition(s) that a person must believe about Jesus in order to be saved (see pp.107-110).