Method for preparing an adjustable side view mirror mounting mechanism (40,50,70) for vehicles which includes a conventional mounting support (14) supporting neck (12) and mirror (M). After the neck (12) is cut a desired distance above base (14) the neck stub (23) left on base (14) is removed and a replacement sleeve (70) is substituted. A slidable mirror support block (50) has a slot (64) through which is received bar (40) and which has lock means (56) for securing and releasing the block for slidable movement with respect to the bar. On the top of the block means (50) is a support cavity (55) to receive the shortened neck (12) for supporting the mirror (M). The mounting bar (40) with block (50) is attached to the upper end of sleeve (70) to complete the installation.