The city council of a city of the metropolitan class is authorized to issue and sell bonds of the city, from time to time, to finance street improvements, as provided in this section. The amount of bonds which may be issued and sold at any one time shall not exceed the total amount of bona fide contracts actually entered into for the kinds of street improvements included within this section and for the financing of which provisions have not otherwise been made. The proceeds from bonds sold under the authority of this section may be used and employed to finance or to aid in financing the classes and kinds of improvement, inclusive of all proper intersection charges, designated in this section, including paving, repaving, surfacing and renewing surfaces, changing character of paving, guttering, reguttering, curbing and recurbing, improvements made in combination as authorized in section 14-391, and macadamizing streets, avenues, alleys, and public thoroughfares of the city.