Any revenue derived from an increase in the rate of tax provided by Section 39230, as amended by Section 147 of Chapter 36 of the Statutes of 1977, prior to July 1, 1975, and which is unexpended on that date, may be used after July 1, 1975, by the governing board of a school district to complete the corrective structural repair, reconstruction, or replacement of any school building subject to Section 17367 which had not been completed on that date.