AM telescoping mast antenna for FM reception?

[Green Monster]

The clearance into my garage is tight. I have to take my antenna off prior to driving my Blazer into the garage. I came across some repo am telescoping antenna masts for the 67-72 pickups. Started thinking this might be a good idea to replace my solid FM antenna mast for an AM as long as I can still get FM reception through it. Then I can raise it to the height of the windshield and not have to worry about installing and removing my existing antenna. I now have an FM radio in my Blazer. The list of options indicates the Blazer came with an AM radio.